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Altered 7th Chords
The tones most likely to be altered are the 9ths and the 5ths. When playing a 7alt chord, you obviously aren't going to alter the defining tones of the chord ( 3rd & b7 ). This therefore eliminates either the 3rd and the b7th from becoming the object of any alterations. * * * * * * * A natural 4th (11th) note is not considered "altered" because it's the natural extension of tertial harmony. A #11 (#4) note is usually felt as a b5. So we generally don't "alter the 4th (11th)". Lowering the thirteenth is usually felt as sharping the five. (Flat 13th does show up in charts from time to time though.) With the 9th you have two possible alterations: sharp and flat ( # & b ). Same with the 5th: diminished & augmented. That yields four basic possible combinations: 7b5#9 7b5b9 7#5#9 7#5b9 * * * * * * * There doesn't necessarily need to be a "minimum" of 2 alterations. Often one alteration is enough. This yields another 4 choices: 7#5 7b5 7#9 7b9 If we choose to alter the tonic note, its substitute is the #IV. With pianists, the rootless chord crowd uses two voicings as a typical LH accompaniment when encountering a "7alt" chord in a chart: 7#5#9 chord 7 #9 3 #5 The astute observer familiar with rootless chords will notice that the above voicings are the standard ones for the tritone substitute dominant 13th(no 11) chord. For those unfamiliar with the rootless system, here's an example of this variation of G7alt:
This implies that it might be a reasonable strategy (if you have to "think fast" in a live situation) to use the typical rootless tritone substitute when encountering the "7alt" indication. Examples: Db7 analyzed as G7alt = Db [b5th] - F [b7th] - Ab [b9th] - B/Cb [3rd] Db9 analyzed as G7alt = as above, but add D#/Eb [#5th] I wouldn't advocate this as the only and perhaps not the best strategy, but it certainly should be taken into consideration as a serious contender when searching for the "ideal voicing" for an alt7 chord. I have seen instances where both a b9 AND #9 have been
used simultaneously 7b9#9 7b5b9#9 7#5b9#9 The same holds true for double-altered V's: 7b5#5 7b5#5b9 7b5#5#9 * * * * * * * Use of WholeTone scales over alt7 chords: The whole tone scale is often chosen over both 7b5 & 7#5 chords. Omitting the most offensive tone leaves you with a "Lydian" (whole tone scale) style pentatonic mode. Use of Diminished scales over alt7 chords: Over a 7b9 you can use the dim(h-w) scale. For C7alt that would be | C - Db - D# - E - F# - G - A - Bb - C | Each chord tone (except the root) has an accompanying note a half-step below it acting as its leading tone. D# -> E F# -> G A -> Bb * * * * * * * Use of Ascending Melodic Minor Modes over alt7 chords: Construction of the "dimwit" scale (diminished-whole tone / dim-WT) with C as its root: The first four notes are a Diminished Tetrachord: [ H W H = C - Db - D#/Eb - E/Fb ] The second four notes are the Lydian Tetrachord: [partial Whole Tone scale = W W W = F#/Gb - G#/Ab - Bb/A# - C ] Also note that the diminished-wholetone scale is the 7th mode of the Ascending Melodic Minor scale. The dimwit scale is a good candidate for soloing over altered chords. This scale contains all of the possible alterations ( b9 #9 b5 #5 ), and ALL of the defining chord tones ( 1 3 b7 ) too! This scale analyzed over a C7alt chord would be:
If we were to use a #IV7 substitute (F#7) for our C7alt
chord,
If there happens to be a note in there that you like less than others, don't play it so much. * * * * * * * When searching for the perfect alt7 chord, always look to the music itself. Do what the changes and current tonal center suggest to your ear. 7
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