I think perhaps we make too much of the differences between ABC and the 5-line thing ? They're both ways of representing the same concepts - different ways of showing a quaver, a bar-line, a slur, etc (the only significant - to me - difference is ABC's ability to handle more than 2 modes, which from the POV of The Tunes is a big gain). If somebody can read standard notation I'd be surprised if they found it very hard to get to grips with ABC (if they needed to, of course. If somebody doesn't see a need for it, fine, carry on as you are …). And likewise, if somebody works by ear, I'd expect ABC to be about as hard to pick up as standard notation.