One piece of music a month? (5)
I believe the answer is:
march
I believe this is a double definition.
'one piece of music' is the first definition.
(eg a wedding march)
'a month?' is the second definition.
(I know that Mar is a type of Gregorian calendar month)
(Other definitions for march that I've seen before include "Stride; month" , "Month, piece of music" , "Protest; month" , "The month for military movement" , "Walk smartly" .)