Polychords

[bvdp]

I've been having a bit of a dialog with a user who want to use some complex chords with MMA. Simple example is to play a Dmaj chord over a C7. This would mean the notes:

   C  E G Bb D' F#' A'

Right now you can't do that (easily) in mma. Two options are:

 - create a new chord using DefChord

 - use a SOLO track and write the notes in by hand.

Now, the concept of polychords (or hybrid) is not new to music. So, let's add it. Problem is (as so often) is with the notation. The theory I'm familiar with show polychords as a fraction. The chord on top is played higher than the chord on the bottom. So, in the above example we'd have a  D ... C7 (the ... represents the fraction line).

My first suggestion is to use a 'bar' to construct the chord: C7|D

Now, the question comes about the octaves. I'm thinking that rather than forcing a combination I'd force the user to select. So, the duplicate the example we'd have "C7|+D".

It's rather trivial for mma to figure the notes for the 2 chords and then to combine them. A bit harder for the scale notes which are limited to 7. So, in most cases they'd probably just take the values of the 1st chord (ie, do nothing). The chord tones are limited to 8, but that shouldn't be an issue (??). If you end up trying to combine 2 5 note chords you'd just lose some tones at the top end (which could be a warning).

So ... comments?

[zappfinger]

Looks good Bob. I would indeed go for the version where you have to enter the octave.

Also it would be nice to allow 2 different volumes, for the upper and lower chord.
Usually a higher chord gets the impression of sounding louder.
In this case it is nice if the higher chord sounds less loud, making it sound almost like harmonics...

BTW, slightly off topic: this particular chord does almost represent the higher harmonics of a C note (played with an instrument with lots of overtones, of course).

[bvdp]

Having a bit for free time this afternoon (or as some might say, having no life) ... I played a bit with the polychords. Took about a dozen lines of code to add this.

I'll put up a beta/developer version later this week. I do want to test a bit.

But, chords like C7|D will work just fine. Matter of fact, since I'm just doing 2 chord name parsing and adding the results you could even do cool things like C7/G|+D/A ... I'll let you figure the result.

The volumes are not being adjusted by mma. If you need different volumes it'll be easy enough to do by redefining the chord pattern. I think that to assume a volume change might be unnecessary ... esp. when you see what mangling is happening with the different voicings. Also, chord notes are somewhat adjusted already when notes are adjacent.

[Dewdman42]

I think there are simple cases where this feature can also be applicable in a more tonal way.  Sometimes you want the band to play based on extended chord, but you want one particular track to be limited to 3 voice major or minor chord only (no extensions).  Or visa versa, you might want the overall band to be using a simple major or minor chord, but you want one particular track play, for example, some kind of ninth chord.  This feature will make that possible.... In addition to any polychordal things that people might be messing about with.

nice feature.

[bvdp]

More recent versions of MMA support different chords for different tracks ... so you can have the guitar playing a C7 and the piano a C9, etc.