Sound of Music, major effort (6)

I believe the answer is:

strain

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This might be a double definition.

'sound of music major' is the first definition.
'strain' can be an answer for 'sound' (thesaurus). I'm not certain of the 'of music major' bit.

'effort' is the second definition.
(strain is a kind of effort)

Can you help me to learn more?

(Other definitions for strain that I've seen before include "Melody; filter" , "Race" , "Wrench; melody" , "Struggle" , "Great effort - sieve" .)

I've seen this clue in The Telegraph.

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