Questions for this exercise need to have the key
variable set if the key signature is anything else than ''c'' major (or ''a'' minor). Example:
header { module = singchord lesson_id = "a404df62-e037-6a1b-9027-cd05397e88a2" version = "3.1.4" title = "Simple chords" } question { music = "c''|e'|g|c" } question { music = "a'|e'|c'|a" } question { key="d \major" music = "a'|fis'|d'|d"} question { key="f \minor" music = "as'|f'|c'|f"}
See also the section called “Sing chord”.