Lilypond
I have experimented with music score editors for a long time, but none really satisfied me. I have also read about Lilypond years ago, but I didn't really try it out, because programs without Wysiwyg seemed outdated to me (who really still uses TeX anymore?).
However, since none of the free graphical Wysiwyg programs satisfied me (and I refuse to use non-free programs), I finally tried out Lilypond in summer 2011, and it worked from the beginning. It offered solutions for almost all my problems, and for problems I don't have, And for those problems I have no solutions yet, I have the impression that solutions do exist, it's just up to me to find them.
But what do I use Lilypond for? I mostly typeset old songs from our old cheap songbooks. Here is what I do with them:
- transpose songs to different keys, for example if you find it easier to play songs in C major, or if you have instruments that can play only certain keys,
- rearrange songs optically, so the structure becomes clearer,
- try out new unknown songs by listening to the MIDI output,
- compose new or rearrange existing songs with different instruments etc.,
- or just simply archive songs digitally, for me and for others via Internet.
Lilypond comes with an excellent documentation, including many examples and templates. Here are two PDF files I sometimes refer to. Please note that these may be outdated in the meantime; refer to the Lilypond homepage for the current versions.