Good ideas, well presented.

#3, selecting the instrument(s) you want for an effect, rather than the ones you don't, is actually an old request. It has not been vigorously carried forward over the last decade or more, so this is good to see.

Now I'm going to put on my programming professor hat. If implemented, there would have to be a way to enter and display the instruction such that all existing files would still work. You would need an option that toggles the display scheme. I assume the code would then have to be able to show the inverse of the current string of letters; i.e. D7...d (hold all except for drums) becomes D7...bpgs (hold the bass, hold the piano, hold the guitar, and hold the strings, but don't hold the drums) under that system. Not so elegant. But the inverse could sometimes be very nice: D7...bpgs becomes D7...d In other words, whichever system you pick, sometimes you win, sometimes you lose as far as brevity/clarity.

For an option to be able to enter the instruction the way you prefer, +1

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