Jack Campin wrote: There are lots of easily accessible utilities for transposing ABC. It's instantaneous and most of them are very reliable.

If this is in response to me, that's true but not the point I'm making. Can you sing "Do mi sol"? If you had even the minimal training I had, you can. Can you sing "A C# E"? I cannot, without a pitch pipe; I don't have perfect pitch. Sol-fa tells you how to sing a melody; ABC, for singing, requires either perfect pitch or translation into a scale.

Now maybe most people can't use sol-fa for that, because they weren't trained for scale singing in today's music classes. And I couldn't use sol-fa for that in, say, Lydian mode (for two reasons: first, I can't sing a Lydian scale, and second, I don't know how it would be transcribed :-). But the point I'm trying to make is that sol-fa is human-readable (relatively); ABC is less human-readable but more machine-readable.

So which is preferable? If the goal is playback, then ABC; if the goal is sing-back, then maybe sol-fa. :-)