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I can hear that soloing over an A major chord using a B major scale "works" but I am curious as to the musical theory why it works?

I know the C# and E contained in the B major acale are the 3rd and 5th of A major so that makes sense but there is no A in B major.

The G# and A# notes in the B major scale flirt just below the A and just above the A and suggest some type of unresolved tension...?

I suspect this is a large part of the reason why this "works" but I was wondering what is the real music theory behind why you can solo in a major scale a whole step above a major chord?

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  • Have you found something that does NOT work? :) For me personally, playing completely random notes does not work even if all the notes come from a supposedly "correct" scale. It is still nonsensical noise. Random notes from any scale don't work over any chord. There has to be some kind of a musical idea that you do with the notes. In that sense, the fact that notes were selected from a particular scale is not a sufficient reason for the notes to "work".
    – piiperi Reinstate Monica
    Commented Jul 16, 2021 at 13:36
  • Actually, I tried to say, it would be a more meaningful question if you asked, what it is that certain notes played in a certain way over an A major chord do. Scales by themselves don't "work", because it is possible to construct rubbish from the notes of the C major scale that does not "work", even over a C major chord. For something to "work", there is always an assumption of some sort of an artist or designer who uses discretion and artistic choice, and it's the discretion and artistic choice which make things work, not the ingredients as such.
    – piiperi Reinstate Monica
    Commented Jul 16, 2021 at 13:57
  • Funnily enough, using notes from key G major work over an A chord too, in quite a Bluesy way.
    – Tim
    Commented Jul 16, 2021 at 16:27
  • By "work", do you mean that it sounds like you're playing outside (the established chord progression) but it still sounds fine, or do you mean that it still sounds like you're playing over the correct chord?
    – Dekkadeci
    Commented Jul 17, 2021 at 15:25

3 Answers 3

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The B major scale contains B, C#, E, F#, which happen to be all the notes of A major pentatonic, minus the root. The G# is the 7th of A, playing might give the chord an Amaj7 feel. The D# (#11) and the A# (b9) definitely provide some tension, with the former providing a lydian feel, which is common enough in some genres.

My guess is it sounds good because it is A major pentatonic with some added chomatic tensions (but not too many), and is never going to truly resolve back down to A until you switch the scale that you're using

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  • All you have to do is stop playing, and the backing track will provide the resolution to A! :) The total combination of sounding notes will contain an A note because of the backing track. In that sense, it's not even possible to play B major scale over A major, unless you can somehow suck all the A notes out of the backing track. But then it wouldn't be A major anymore.
    – piiperi Reinstate Monica
    Commented Jul 16, 2021 at 14:04
  • As a fairly inexperienced amateur, I notice the "too many roots" problem when soloing. That is, I end up playing the root of my chord in places where I don't necessarily want my phrase to end, and I don't find that too sonically pleasing. Soloing using notes from a pentatonic/majors scale a whole step above the root seems like a good idea. I'll have to try it next time I'm around my instrument
    – Awalrod
    Commented Jul 16, 2021 at 14:13
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...soloing over an A major chord using a B major scale "works"...

Define "works." Anything can "work."

A major and B major scale only differ by two sharps, D and A sharp.

Common tones are B C# E F# G# - which superficially looks like an E major pentatonic scale. That set of tones over both an A major or B major chord give flavorings of maj7, add6, and add9.

...but there is no A in B major...

Right. The A is A#.

By typical chord/scale matching a B major scale to a A major chord does not really work.

A lot of things "working" can be explained in terms of modal flavoring or altered tones. For example, a lowered seventh scale degree can give a mixolydian modal flavor, or raising/lowering the ninth or fifth of a dominant ninth chord makes it altered. There is also something called a chromatic cross relationship, but that is usually seen with the leading tone or third of a scale. In the case of an A major chord with a B major scale, the root or the chord is "altered" by the scale. It doesn't really "work" by the conventional means of introducing chromatic tones.

This is where describing something as "works" is too vague. At least too vague to call music theory. To the extent that A# doesn't "work" you might be better off playing E major to get an A natural. The only differing tone will be the D# which will give a lydian flavor to the A major chord.

If the A# is handled carefully, you can mitigate the dissonance. Play it less, shorter durations, in metrically weak positions, and it will lessen the mismatch.

If "works" means polytonality, then it's a completely different ball game. You then embrace the clash of hearing A major and B major simultaneously and sound like a modern, someone like Darius Milhaud, or Stravinsky.

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I was listening to a musical cadence of A maj to F# maj. The melody run in the A measures sounded intriguing to me and I knew there was something "different" about it so I transcribed it. (Wanted to include the transcription in this comment but doesn't seem as though attachments are allowed.) Basically it started on low C#, went all the way up to a high G# before it came back and ended on a C# an octave above the starting C#. When I examined it, I was very surprised to see, (except for a "G" passing tone in a "F#,G,G#"), sequence, it was simply a melodic run in B maj. It was a perfect melodic sequence over A maj that lead naturally to the F# maj cadence where of course continuing the B maj melodic scale worked just fine modally. For the A maj part of the cadence I can certainly understand how starting and ending on the C# (3rd of A) works and I can also feel how "bookending" the A with a G# and A# but never actually playing the A teases the ear with A without ever really resolving to it. I myself just never would have thought to use B maj over the A maj. Just wondering if I finally discovered something Bach already did 350 years ago....

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