student question: append-map

[David Garfinkle]

Hey Lilydevs,

Can't seem to find any code examples of the Scheme function (append-map f
list1 list2) online, and I can't seem to call it correctly at all. Could
anyone show me how it works?

lilypond scheme-sandbox

map works fine:
(map double '(1 2 3))
=> (2 4 6)

can't use append-map:
(append-map double '(1 2 3))
=> Wrong type in position 1 (expecting empty list) (wrong-type-arg)

this is in the context of trying to copy/edit music->make-music in
music-functions.scm