One band or another being heard (6)
I believe the answer is:
troupe
'one band' is the definition.
(I've seen this before)
I don't understand how the rest of the clue works.
(Other definitions for troupe that I've seen before include "travelling band" , "Travelling company of performers" , "Group of performers" , "Company of theatrical performers" , "A company of actors or acrobats" .)