+ (glissandoMap ,list? "A map in the form of '((source1 . target1)
+(source2 . target2) (sourcen . targetn)) showing the glissandi to
+be drawn for note columns. The value '() will default to '((0 . 0)
+(1 . 1) (n . n)), where n is the minimal number of note-heads in
+the two note columns between which the glissandi occur.")