Options are @code{'text} and @code{'hairpin}.")
(span-text ,markup? "The displayed text for dynamic text
spanners (e.g., cresc.)")
- (spanner-id ,string? "Identifier to distinguish concurrent spanners.")
+ (spanner-id ,key? "Identifier to distinguish concurrent spanners.")
(start-callback ,procedure? "Function to compute the negative length
of starting grace notes. This property can only be defined as initializer
in @file{scm/@/define-music-types.scm}.")