I sing in an amateur choir of 15 or so people singing renaissance (mostly) and medieval (a little) music.
I used to lead an eclectic folk-music group in which I sang, played hammer dulcimer, occasionally played other instruments, and arranged and composed music.
In 1997 I co-authored Joy and Jealousy, a book reconstructing the music and dances for the 15th-century-Italian balli, about two-dozen set dances. I reconstructed melody lines for the dances working from primary sources and informed by other researchers, and I wrote arrangements of all of them suitable for amateur recorder consorts. (I know that recorders aren't the most authentic instruments for this repertoire, but they're common and the goal of this work was to help people actually dance these dances.)