1998wdt

THE SCALES:

FOR SPANISH GUITAR REMEMBER THIS:  THE PRACTICAL MAJOR SCALE SUBSTITUTION FRETBOARD MATH LAYOUT IS TOTALLY DIFFERENT FROM THE 6th CHORD SUBSTITUTION MATH LAYOUT except when you use the Steel Guitar method of simply sliding the 6th chord back and forth between the base chord and it's extensions.  The reason for this is because PRACTICAL scales on the Spanish Guitar are achievable with frets whereas the Steel Guitar has no frets and is restricted to the note voicings and inversions of it's tuning applied by the straight steel bar up and down the neck.   The reason we will use 2 different maths for the Spanish Guitar is because
the 6th
chord based chord substitution method is based upon the
Mixolydian (dom7)
mode and the Major scale we will use for SCALE substitution is based upon the Ionian (Maj7) mode which will become apparent as you analyze this course.  Although you CAN play scales, passages and harmonies using the Steel Guitar techniques for chord and extensions positions, simply by using the 6th chord fingering like the Steel Guitar uses the steel-bar,  you will still need / want to know the Major 7 scale substitution positions for soloing more broadly with Spanish Guitar techniques.  But don't get big headed against Lap Steel Guitar, because Lap Steel can do just as many things Spanish Guitarists can only dream about!

THERE ARE 2 MATH TEMPLATES YOU MUST REMEMBER FOR SCALES:
See figure 092601-4 and follow along or refer to it:

Using the word "template", I mean a very simple order of parameters that can be used in any circumstance to calculate and/or map out mode structure.  Though you will have to memorize the templates, you will also need them to remind you if you forget, or use for review etc.

(1)  THE MAJOR SCALE STEP TEMPLATE:

This might sound complicated at first;  But we will combine the different templates as we go along into a very clear and simple picture of how they show the same thing in different manners;  So that when we are finished you will only have to memorize 1 to get all the others.  For now you need to know how they are derived.

1 fret on a Guitar is 1/2 step;  2 frets are 1 whole step.  The steps between the notes in a Major scale are:  Starting from 1, whole step to 2, whole step to 3, half step to 4, whole step to 5, whole step to 6, whole step to 7, half step to 8/1.  Every octave will be the very same repetitive sequence.  The easy way to remember it is:  W W h W W W h (Whole Whole half Whole Whole Whole half).  THIS IS THE REPEATING MAJOR SCALE STEP SEQUENCE TEMPLATE, .AND IT IS CONGRUENT THROUGHOUT THE ENTIRE MODE STRUCTURE,  IN EVERY KEY.   SO JUST MEMORIZE W W h W W W h .and realize that it repeats itself through all octaves  like W W h W W W h W W h W W W h W W h W W W h ..etc etc.  All the common Major and minor scales and chords are contained in this sequence.

(2)  THE MODE SCALE SUBSTITUTION TEMPLATE.  THIS IS THE ONE YOU WILL HAVE TO MEMORIZE.  The entire modal system is said in this template;  We just have to learn what it means.

I Maj7 (Ionian)
IImin7 (Dorian)
IIImin7b2b6 (Phrygian)
IV#4 (Lydian)
V7 (Mixolydian)
VImin7b6 (Aolean)
VIImin7b2b5b6 (1/2dim) (Locrian)

THE Maj7 IONIAN WILL BE THE "MOTHER" FOR THE SCALES TEMPLATE.
All of these mode scales are identical notes derived from their Ionian Maj7 "Mother" (relative Maj) scale notes.  They apply in any key, or any one of them being of whatever specific key or root note we want to assign, which would of course change their common relative Major scale;  That's what is remarkable about the number system used with modes;  It all applies to any key, scale or chord we desire to reference ANY PART OF mode structure to !

If we applied the above template to G Maj scale or to the key of GMaj, we would get:

GMaj7 (Ionian) = Amin7 (Dorian) = Bmin7b2b6 (Phrygian) = C#4 (Lydian) = D7 (Mixolydian) = Emin7b6 (Aolean) = F#min7b2b5b6 (1/2dim) (Locrian).

They are all the notes of GMaj.

NOW CHECK THIS OUT CLOSELY:  I want you to answer this question in 3 seconds:  What are the notes of D7 scale?

MAYBE 1 in a thousand good Musicians could answer that question in 3 seconds.  But look at the last modal template we just went over.  If you know the modal template you could go right to GMaj7 scale to play D7 scale in less than 3 seconds without even computing what notes are in D7 !

Now answer this question in 5 seconds:  What are the notes of Bmin7 scale?

If you know the modal template you could go right to AMaj7 scale to play Bmin7, because you would know that the min7 root is always up 1 whole step from the Maj7 root and therefore the Maj7 root is always down 1 whole step from the min7 root !  And I do believe that a guitarist with even the most basic guitar knowledge can find a root note on the 6th string to play one simple Maj7 scale off of ! .and certainly within 3 seconds with just a little bit of practice !

Now look at the last template we did above.  You will see included in the modes are Maj, min7, min7b9, Maj#4, dominant 7, min7b6 (the pure minor) and diminished.  And folks that just about fills up a musician's arsenal of scales!  That only leaves augmented to cover by far the vast majority of popular music !  And though augmented is not part of the modal system, it is simply an all whole step notes scale ..so there .now your arsenal will be almost completely full when we finish this course.

Now go STUDY figure 092601-4 again, and try to identify there what we've learned so far.

________________________________________________________________

THE MAJOR 7 SCALE / MODE "SLIDE RULE".

The Major 7 scale / mode template chart in figure 092601-4 and 092701-1 are excellent charts to study to help become familiar with, practice and memorize the slide rule template.
________________________________________________________________

MORE ABOUT MODES:

This course and it's techniques are obviously based upon modes.  In dealing with scales and their notes and subsequent chords, it is extremely beneficial to know what modes are.  I will be repetitive in this section and cover the idea from several angles. Modes are actually quite simple but guiding the studies can seem and sometime be complex in covering the abstract that leads to understanding modes' simplicity..  I advise and invite you to take this course slow and careful if and when it or sections of it seem confusing or complicated.  Remember the "read 5 times" trick.

Recapping modes and different perspectives:  See figures 092301-1 and
092601-1
, 092601-2 and 092601-3.  There are seven common modes with specific names we saw in the previous chords sections.  Each mode is simply an identifying name that works in any key to keep track of each mode's scale, derived from their relative Major scale just like explained in the above sections on scale steps.  First let's start with C Major scale:  The notes are C, D, E, F, G, A, B, C.  Again, the steps between the notes are W W h W W W h.  But you must remember that we are dealing with many octaves in music so the sequence simply repeats itself for many octaves, and must be thought of more like this (not covering all octaves): 
W W h W W W h W W h W W W h W W h W W W h W W h W W W h

The note numbers of ANY scale are 1, 2, 3, 4, 5, 6, 7, 1, 2, 3, 4, 5, 6, 7, 1, 2, 3, 4, 5, 6, 7, 1.......... and represent the notes of any scale, upon which sharps or flats are added to change the scale to a specific type.  For instance, a simple minor scale has a b3;  and a minor 7 scale has a b3 and a b7.  Notice there are not any sharps or flats in C Major scale LETTERS nor in it's NUMBERS, nor in ANY Major 7 scale NUMBERS.  This can be confusing because the Major scales of every key except C will require sharps or flats to make the note LETTERS conform to the Major scale step sequence although any Major 7 scale's NUMBER sequence will NOT have any sharps or flats.  The number system itself is used so that not only can it be applied to any key, chord, scale etc .but more pointedly so a Musician doesn't have to bother with the additional sharps and flats required of the note LETTER system.  For instance, G Major scale LETTERS are G, A, B, C, D, E, F#, G (with 1 #);  BUT we can also say the same thing by saying G Major scale is notes 1, 2, 3, 4, 5, 6, 7, 1 (no sharps).  More appropriately we can say that ANY Major 7 scale is 1, 2, 3, 4, 5, 6, 7, 1.  Don't go any further until you understand this paragraph.

See figure 092301-1:  Now let's use C Major scale notes but start on D as root instead of C as root:   D, E, F, G, A, B, C, D.  Those steps (THINK FRETS) are W h W W W h W definitely not a Major scale BUT IT IS THE SAME SEQUENCE, ONLY WITH THE FIRST STEP MOVED FROM C UP TO D MAKING C THE LAST NOTE OF THE SEQUENCE RATHER THAN THE FIRST.  If you don't understand this, look back at figure 092301-1.  The Major 7 scale NUMBERS "slide rule" template just shifted up 1 whole step so the 2nd note D in the C Major 7 scale just became the root (1st note) in the D scale (and C moved down from 8/1 note to become the 7 note).  So far so good.  Now let's combine the new D scale notes, steps and scale numbers and see what happens:  D/1 - W - E/2 - h - F/b3 - W - G/4 - W - A/5 - W - B/6 - h - C/b7 - W - D/1.   There are now 2 flats in the NUMBERS sequence  dictated by the note and step sequence SINCE THE STEPS AND NOTES OF THE "MOTHER" RELATIVE MAJOR SCALE ALWAYS REMAIN THE SAME THROUGHOUT THE MODES FOR THAT SCALE.  AGAIN, the notes and steps of the "MOTHER" Ionian Major 7 scale always remain the same, and while the scale NUMBERS of the subsequent derivative mode scales and their root chords change to conform to the "MOTHER" Ionian NOTES / STEPS.  We can clearly see why this D scale is a minor7 (b3 and b7).  THE MOTHER RELATIVE MAJOR SCALE DICTATES IT;  That's what modes are all about;  The "Mother" relative Major scale notes remain the same and thus inherently dictate each mode's NUMBER SCALE to produce all the different modes' different scales whereby we assign new scale numbers with appropriate flats to be able to comprehend the changes in the scales.  So the D scale numbers that match the C major scale notes / steps are 1, 2, b3, 4, 5, 6, b7, 1, which is a minor 7 scale, the Dorian mode.  This SHOWS us that using C Major notes creates D minor 7 because the C notes make the D scale 3 and 7 notes flatted.  Similarly, assigning / thinking-of the 2nd note in any MAJOR 7 scale as being a root note establishes a min7 scale, and is called the Dorian mode.  If it were the 2nd note of a G Major scale , then it would be Amin7 called 'A' Dorian mode.  Each mode is similarly derived from each successive note / step in the relative Major scale, and will require some of the numbers to be flatted to match the relative Major scale notes / steps.  What will result from this course is that you will not have to consciously deal with what all the numbers in each mode are doing but only what kind of scale you desire; .because the essence of this course is playing the MOTHER Major7 scale as a dead on substitution rather than having to memorize a different scale and all it's math for every type of mode and chord !

Now let's grasp a simple idea.  If minor 7 is derived from the 2nd note of a Major scale, then the 1st note of that Major scale root note will ALWAYS be a bVII of the min7 root, .because we have learned that min7 is Dorian and we've learned what makes Dorian.   So if we want to play Gmin7 scale, all we have to do is play FMaj7 scale because not only is G the 2nd note of F from which Dorian comes from, but F is also the b7 note of the Gmin7 Dorian scale and therefore where the Major 7 scale root is located in a minor7 scale no matter what letter names for the notes are.  If you don't grasp this, read this paragraph before moving on; and remember the "5 times" trick.

HOW THE 5 MOST COMMON MODES SOUND:

Ionian, Maj7, (The doe, rey, me song;  Magnolia;  Don't let the Sun Catch You Crying;  Harbor Lights;  etc.);

Dorian, min7, (BASIS FOR THE BLUES SCALE;  much of Carlos Santana's style;  foundation of most Major and minor blues;  jam over any minor or Major
with much color mode;  foundation for much of those moody minors used by The Doors);

Mixolydian, dom7; (used the most in popular music;  classic Country and Western;  Wooly Bully;  Wipeout;  accentuates dominant 7 notes;  etc.);

Aolean, min7b6; (another "Carlos Santana" favorite;  God Rest Ye Merry Gentlemen, Hit the Road Jack,  pure minor mode for very melodic minor passages that work well with any kind of minor accompaniment or soloing over Major accompaniment, jam any major or minor key);

Locrian, min7b5b6b9, (1/2 diminished mode with b7 present rather than bb7 of full diminished;  works as diminished anyway).

Try having a strumming partner play the triad chord of any mode while you experiment around with the Ionian notes.  Do this for all modes.

Remember the "5 times" technique?

Click HERE to go to the next section,  SUBSTITUTION.






THE SCALES:

FOR SPANISH GUITAR REMEMBER THIS:  THE PRACTICAL MAJOR SCALE SUBSTITUTION FRETBOARD MATH LAYOUT IS TOTALLY DIFFERENT FROM THE 6th CHORD SUBSTITUTION MATH LAYOUT except when you use the Steel Guitar method of simply sliding the 6th chord back and forth between the base chord and it's extensions.  The reason for this is because PRACTICAL scales on the Spanish Guitar are achievable with frets whereas the Steel Guitar has no frets and is restricted to the note voicings and inversions of it's tuning applied by the straight steel bar up and down the neck.   The reason we will use 2 different maths for the Spanish Guitar is because
the 6th
chord based chord substitution method is based upon the
Mixolydian (dom7)
mode and the Major scale we will use for SCALE substitution is based upon the Ionian (Maj7) mode which will become apparent as you analyze this course.  Although you CAN play scales, passages and harmonies using the Steel Guitar techniques for chord and extensions positions, simply by using the 6th chord fingering like the Steel Guitar uses the steel-bar,  you will still need / want to know the Major 7 scale substitution positions for soloing more broadly with Spanish Guitar techniques.  But don't get big headed against Lap Steel Guitar, because Lap Steel can do just as many things Spanish Guitarists can only dream about!

THERE ARE 2 MATH TEMPLATES YOU MUST REMEMBER FOR SCALES:
See figure 092601-4 and follow along or refer to it:

Using the word "template", I mean a very simple order of parameters that can be used in any circumstance to calculate and/or map out mode structure.  Though you will have to memorize the templates, you will also need them to remind you if you forget, or use for review etc.

(1)  THE MAJOR SCALE STEP TEMPLATE:

This might sound complicated at first;  But we will combine the different templates as we go along into a very clear and simple picture of how they show the same thing in different manners;  So that when we are finished you will only have to memorize 1 to get all the others.  For now you need to know how they are derived.

1 fret on a Guitar is 1/2 step;  2 frets are 1 whole step.  The steps between the notes in a Major scale are:  Starting from 1, whole step to 2, whole step to 3, half step to 4, whole step to 5, whole step to 6, whole step to 7, half step to 8/1.  Every octave will be the very same repetitive sequence.  The easy way to remember it is:  W W h W W W h (Whole Whole half Whole Whole Whole half).  THIS IS THE REPEATING MAJOR SCALE STEP SEQUENCE TEMPLATE, .AND IT IS CONGRUENT THROUGHOUT THE ENTIRE MODE STRUCTURE,  IN EVERY KEY.   SO JUST MEMORIZE W W h W W W h .and realize that it repeats itself through all octaves  like W W h W W W h W W h W W W h W W h W W W h ..etc etc.  All the common Major and minor scales and chords are contained in this sequence.

(2)  THE MODE SCALE SUBSTITUTION TEMPLATE.  THIS IS THE ONE YOU WILL HAVE TO MEMORIZE.  The entire modal system is said in this template;  We just have to learn what it means.

I Maj7 (Ionian)
IImin7 (Dorian)
IIImin7b2b6 (Phrygian)
IV#4 (Lydian)
V7 (Mixolydian)
VImin7b6 (Aolean)
VIImin7b2b5b6 (1/2dim) (Locrian)

THE Maj7 IONIAN WILL BE THE "MOTHER" FOR THE SCALES TEMPLATE.
All of these mode scales are identical notes derived from their Ionian Maj7 "Mother" (relative Maj) scale notes.  They apply in any key, or any one of them being of whatever specific key or root note we want to assign, which would of course change their common relative Major scale;  That's what is remarkable about the number system used with modes;  It all applies to any key, scale or chord we desire to reference ANY PART OF mode structure to !

If we applied the above template to G Maj scale or to the key of GMaj, we would get:

GMaj7 (Ionian) = Amin7 (Dorian) = Bmin7b2b6 (Phrygian) = C#4 (Lydian) = D7 (Mixolydian) = Emin7b6 (Aolean) = F#min7b2b5b6 (1/2dim) (Locrian).

They are all the notes of GMaj.

NOW CHECK THIS OUT CLOSELY:  I want you to answer this question in 3 seconds:  What are the notes of D7 scale?

MAYBE 1 in a thousand good Musicians could answer that question in 3 seconds.  But look at the last modal template we just went over.  If you know the modal template you could go right to GMaj7 scale to play D7 scale in less than 3 seconds without even computing what notes are in D7 !

Now answer this question in 5 seconds:  What are the notes of Bmin7 scale?

If you know the modal template you could go right to AMaj7 scale to play Bmin7, because you would know that the min7 root is always up 1 whole step from the Maj7 root and therefore the Maj7 root is always down 1 whole step from the min7 root !  And I do believe that a guitarist with even the most basic guitar knowledge can find a root note on the 6th string to play one simple Maj7 scale off of ! .and certainly within 3 seconds with just a little bit of practice !

Now look at the last template we did above.  You will see included in the modes are Maj, min7, min7b9, Maj#4, dominant 7, min7b6 (the pure minor) and diminished.  And folks that just about fills up a musician's arsenal of scales!  That only leaves augmented to cover by far the vast majority of popular music !  And though augmented is not part of the modal system, it is simply an all whole step notes scale ..so there .now your arsenal will be almost completely full when we finish this course.

Now go STUDY figure 092601-4 again, and try to identify there what we've learned so far.

________________________________________________________________

THE MAJOR 7 SCALE / MODE "SLIDE RULE".

The Major 7 scale / mode template chart in figure 092601-4 and 092701-1 are excellent charts to study to help become familiar with, practice and memorize the slide rule template.
________________________________________________________________

MORE ABOUT MODES:

This course and it's techniques are obviously based upon modes.  In dealing with scales and their notes and subsequent chords, it is extremely beneficial to know what modes are.  I will be repetitive in this section and cover the idea from several angles. Modes are actually quite simple but guiding the studies can seem and sometime be complex in covering the abstract that leads to understanding modes' simplicity..  I advise and invite you to take this course slow and careful if and when it or sections of it seem confusing or complicated.  Remember the "read 5 times" trick.

Recapping modes and different perspectives:  See figures 092301-1 and
092601-1
, 092601-2 and 092601-3.  There are seven common modes with specific names we saw in the previous chords sections.  Each mode is simply an identifying name that works in any key to keep track of each mode's scale, derived from their relative Major scale just like explained in the above sections on scale steps.  First let's start with C Major scale:  The notes are C, D, E, F, G, A, B, C.  Again, the steps between the notes are W W h W W W h.  But you must remember that we are dealing with many octaves in music so the sequence simply repeats itself for many octaves, and must be thought of more like this (not covering all octaves): 
W W h W W W h W W h W W W h W W h W W W h W W h W W W h

The note numbers of ANY scale are 1, 2, 3, 4, 5, 6, 7, 1, 2, 3, 4, 5, 6, 7, 1, 2, 3, 4, 5, 6, 7, 1.......... and represent the notes of any scale, upon which sharps or flats are added to change the scale to a specific type.  For instance, a simple minor scale has a b3;  and a minor 7 scale has a b3 and a b7.  Notice there are not any sharps or flats in C Major scale LETTERS nor in it's NUMBERS, nor in ANY Major 7 scale NUMBERS.  This can be confusing because the Major scales of every key except C will require sharps or flats to make the note LETTERS conform to the Major scale step sequence although any Major 7 scale's NUMBER sequence will NOT have any sharps or flats.  The number system itself is used so that not only can it be applied to any key, chord, scale etc .but more pointedly so a Musician doesn't have to bother with the additional sharps and flats required of the note LETTER system.  For instance, G Major scale LETTERS are G, A, B, C, D, E, F#, G (with 1 #);  BUT we can also say the same thing by saying G Major scale is notes 1, 2, 3, 4, 5, 6, 7, 1 (no sharps).  More appropriately we can say that ANY Major 7 scale is 1, 2, 3, 4, 5, 6, 7, 1.  Don't go any further until you understand this paragraph.

See figure 092301-1:  Now let's use C Major scale notes but start on D as root instead of C as root:   D, E, F, G, A, B, C, D.  Those steps (THINK FRETS) are W h W W W h W definitely not a Major scale BUT IT IS THE SAME SEQUENCE, ONLY WITH THE FIRST STEP MOVED FROM C UP TO D MAKING C THE LAST NOTE OF THE SEQUENCE RATHER THAN THE FIRST.  If you don't understand this, look back at figure 092301-1.  The Major 7 scale NUMBERS "slide rule" template just shifted up 1 whole step so the 2nd note D in the C Major 7 scale just became the root (1st note) in the D scale (and C moved down from 8/1 note to become the 7 note).  So far so good.  Now let's combine the new D scale notes, steps and scale numbers and see what happens:  D/1 - W - E/2 - h - F/b3 - W - G/4 - W - A/5 - W - B/6 - h - C/b7 - W - D/1.   There are now 2 flats in the NUMBERS sequence  dictated by the note and step sequence SINCE THE STEPS AND NOTES OF THE "MOTHER" RELATIVE MAJOR SCALE ALWAYS REMAIN THE SAME THROUGHOUT THE MODES FOR THAT SCALE.  AGAIN, the notes and steps of the "MOTHER" Ionian Major 7 scale always remain the same, and while the scale NUMBERS of the subsequent derivative mode scales and their root chords change to conform to the "MOTHER" Ionian NOTES / STEPS.  We can clearly see why this D scale is a minor7 (b3 and b7).  THE MOTHER RELATIVE MAJOR SCALE DICTATES IT;  That's what modes are all about;  The "Mother" relative Major scale notes remain the same and thus inherently dictate each mode's NUMBER SCALE to produce all the different modes' different scales whereby we assign new scale numbers with appropriate flats to be able to comprehend the changes in the scales.  So the D scale numbers that match the C major scale notes / steps are 1, 2, b3, 4, 5, 6, b7, 1, which is a minor 7 scale, the Dorian mode.  This SHOWS us that using C Major notes creates D minor 7 because the C notes make the D scale 3 and 7 notes flatted.  Similarly, assigning / thinking-of the 2nd note in any MAJOR 7 scale as being a root note establishes a min7 scale, and is called the Dorian mode.  If it were the 2nd note of a G Major scale , then it would be Amin7 called 'A' Dorian mode.  Each mode is similarly derived from each successive note / step in the relative Major scale, and will require some of the numbers to be flatted to match the relative Major scale notes / steps.  What will result from this course is that you will not have to consciously deal with what all the numbers in each mode are doing but only what kind of scale you desire; .because the essence of this course is playing the MOTHER Major7 scale as a dead on substitution rather than having to memorize a different scale and all it's math for every type of mode and chord !

Now let's grasp a simple idea.  If minor 7 is derived from the 2nd note of a Major scale, then the 1st note of that Major scale root note will ALWAYS be a bVII of the min7 root, .because we have learned that min7 is Dorian and we've learned what makes Dorian.   So if we want to play Gmin7 scale, all we have to do is play FMaj7 scale because not only is G the 2nd note of F from which Dorian comes from, but F is also the b7 note of the Gmin7 Dorian scale and therefore where the Major 7 scale root is located in a minor7 scale no matter what letter names for the notes are.  If you don't grasp this, read this paragraph before moving on; and remember the "5 times" trick.

HOW THE 5 MOST COMMON MODES SOUND:

Ionian, Maj7, (The doe, rey, me song;  Magnolia;  Don't let the Sun Catch You Crying;  Harbor Lights;  etc.);

Dorian, min7, (BASIS FOR THE BLUES SCALE;  much of Carlos Santana's style;  foundation of most Major and minor blues;  jam over any minor or Major
with much color mode;  foundation for much of those moody minors used by The Doors);

Mixolydian, dom7; (used the most in popular music;  classic Country and Western;  Wooly Bully;  Wipeout;  accentuates dominant 7 notes;  etc.);

Aolean, min7b6; (another "Carlos Santana" favorite;  God Rest Ye Merry Gentlemen, Hit the Road Jack,  pure minor mode for very melodic minor passages that work well with any kind of minor accompaniment or soloing over Major accompaniment, jam any major or minor key);

Locrian, min7b5b6b9, (1/2 diminished mode with b7 present rather than bb7 of full diminished;  works as diminished anyway).

Try having a strumming partner play the triad chord of any mode while you experiment around with the Ionian notes.  Do this for all modes.

Remember the "5 times" technique?

Click HERE to go to the next section,  SUBSTITUTION.





Lesson 3.  Scale Templates.
Lesson 3.  Scale Templates.
.   2  .   3  4  .   5  .   6  .   7  1   .  2
.   2 b3 .   4  .   5  .   6 b7  .  1
W     W   h    W    W    W   h
W     W   h    W    W    W   h
1998wdt