Having trouble with last 3
13d "Roll up to study very old instrument" (9)
C?N?O?U?A - presumably name of an old musical instrument but can't see it
19a "The way to tackle long instrument" (6)
S?I?E? - SPINET would be in keeping with theme but can't see the parsing
10a "Group in the other marquee forget note" (6)
?E?T?T - SEPTET would fit the theme but again can't parse
Any help greatly appreciated