[bonzini]

I use it to typeset songs that my son wants to learn on the guitar. I can tailor the difficulty and add some "special" things based on what he's learning, for example customizing chords or changing the key signature.

I also used it to typeset a simple song that I arranged and played at a funeral service. I could have written it by hand, but given I was a bit anxious about the performance it helped to have an extremely readable version.

Writing lilypond source code is about the same difficulty as LaTeX. The midi output helps stomping out mistakes and it's easy to follow the source as it plays. Sheet music is pretty expressive, it's a good balance between showing what to play and how, and lilypond is about 1:1 with sheet music.

That said in lilypond you can add some kind of abstraction through both macros and typesetter settings. For example it can calculate automatically which frets and strings correspond to notes, and generate guitar tablature (fret+string notation) and sheet music from the same source. Also, instead of specifying by hand how to play each note, you can basically tell lilypond "I want the left hand to be roughly here on the fretboard" and that affects the strings it tells the player to pluck.