Crossword Genius

Spooner gets B, D#, F# permutations from these instruments (9)

Ross

I believe the answer is:

keyboards

'these instruments' is the definition.
(I've seen this before)

I don't understand how the rest of the clue works.

(Other definitions for keyboards that I've seen before include "Electronic pianos" , "Instruments" , "have computers at their fingertips here" .)

I've seen this clue in The Guardian.
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