Audio of really bassy music performance? (4)

I believe the answer is:

solo

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'performance?' is the definition.

I can't explain the rest of the clue.

(Other definitions for solo that I've seen before include "Lone" , "One-person performance" , "It's performed alone" , "By oneself" , "Done by one person" .)

I've seen this clue in the Sydney Morning Herald.

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