This is an amazing and spectacular mod. I'd really love to see oboe support if you could, I know its a bit out there but if you ever get around to doing woodwinds, it'd be cool. Also another suggestion could be music sheets? (I know you could just grab a music sheet and do it that way). Other than that keep it up this mod rocks and is the single most creative mod I've ever seen.
Maybe replace the strong recipies with enforced string from spiders? Maybe just 3 spider string makes one enforced string? Just thought iron seemed kinda out of place, but it's a minor complaint. Love the mod. For the next instrument, maybe a brass instrument? Trumpet, or something like that (Or, a Tuba, if you feel like going on a modeling adventure :3)