Cheap wedding ring that plays tunes (5,4)
I believe the answer is:
brass band
'that plays tunes' is the definition.
(a brass band is a musical group)
'cheap wedding ring' is the wordplay.
'cheap wedding' becomes 'brass' (I can't explain this - if you can you should give a lot more credence to this answer).
'ring' becomes 'band' (synonyms).
'brass'+'band'='BRASS BAND'
(Other definitions for brass band that I've seen before include "Group of wind instruments" , "on hand at cheap wedding?" , "Group of musicians, maybe military" , "Group with trumpets etc" , "cheap alternative to gold ring" .)