Help from a musican sought

Interesting idea! Just a couple of notes:

2. Since you seem to actually be talking about seventh chords and not triads, be aware that V is a dominant seventh, not a major seventh like I and IV (all are major triads, though). Dominant seventh uses 10 instead of 11 (insert Spinal Tap joke here :-).

Also, FWIW, you can often determine a useful chord to place on other roots, but it takes a certain amount of ingenuity. For instance, a chord built on 1 is probably diminshed if resolving up to 2, dominant seventh if resvolving down to 0. Actually, that rule - diminshed if resolving up by 1, dominant if resolving down by 1 - is useful for other scale degrees too, although diminshed chords resolving down by 1 are common on 3 and 8. The most common resolution for chords built on scale degrees other than those you have listed, though, is down by 7 (= up by 5). In that case, use dominant seventh if the target chord is minor and vice versa. And to really make the results seem more natural, consider making the chords on 4, 9, and 11 dominant if they are resolving down by 7 / up by 5 to minor chords. At least sometimes, for variety.

Maybe this is more than you want to deal with, but you did ask.

3. The chord you list is actually half-diminished, not fully diminished. Both types can happen on 11, and the half-diminished fits the scale better, but the fully diminshed may be more common, at least when resolving to 0. But dominant seventh is probably more common, as this chord is more likely to reaolve to a mimor chord on 4.

4. You are correct anout the seventh - it's the same regardless of inversion. I'm not sure, though, what "base" and
"strings" are supposed to indicate here. One of the opportunities for a little creativity in writing this algorithm would be for the program to figure out the most appropriate voicing based on creating the smoothes voice leading from the previous chord, as opposed to having the user select it from a limited palette. Because all sorts of possibilities exist - RTF, RFT, TFR, TRF, FRT, FTR just for triads, and that many more when including sevenths.

Could I make a suggestion for a plug-in that would get you in the correct area and would certainly help me?

I've been posting some tunes for accordion to musescore.com. http://musescore.com/cwhysall/scores/34526 is one example. In accordion music there is a convention that the chords in the left hand are not fully spelled out; only the root note is indicated. The type of chord is indicated above the staff where necessary (I always put all of the chord names. It helps me as a guitarist).

The convention is also that root notes are indicated with their stem down, chords are indicated with stem up.

There are only four chord types available on the Stradella system, major, minor, dominant 7 and diminished. These chords are all created within a single octave. This means that some are in root position, some are in first and some in second inversion. You can get the full story here: http://upload.wikimedia.org/wikipedia/commons/8/8c/120-button_Stradella…

The plug-in that I would like is one that works through the score completing the chords according to the above chart so I could hear the proper effect. It would be brilliant if the notes that aren't shown by the convention were also invisible.

I think this would be a useful plug-in from your point of view because the basic mechanism for working through a score would be much the same. Even the way chords are formed could remain because the unique advantage of the Stradella system is that voice-leading is more-or-less automatic. If you don't like it you can't do anything about it anyway!

Voice-leading is important to produce sensible harmony, and you would need to accomodate it in your plug-in for it to be really useful. This plug-in would certainly get you on the way.

I hope you like this idea.

--
colin

Lots of theory to install in this plugin..

but... It still comes down to the user to specify what he/she wants.

If you don't know how chords work this is also one area where it would be interesting to approach from a brand new angle.

Assuming the urser does not know what a minor/major/7th/augmented chord ect can sound like,... Why not also specify more human associations with each option as a sort of semi automated selection.

eg.

1) You plant your root note
2) fire up the plugin
3) select from

* Normal
* Sad
* Passing
* Extra
* Strange

So, with 5 basic options the plugin would decide how to achieve the described result. ??????

Normal = Major Chords
Sad = Minor Chords
Passing = Passing Chords
Extra = 7ths / 9ths
Strange = Augmented/Dissonant

ermm... or something like that.