Method of teaching singing, complicated solo in fact (5,3-2)

I believe the answer is:

tonic sol-fa

'method of teaching singing' is the definition.

'complicated solo in fact' is the wordplay.
'complicated' is an anagram indicator.
'solo'+'in'+'fact'='soloinfact'
'soloinfact' is an anagram of 'TONIC SOL-FA'.

(Another definition for tonic sol-fa that I've seen is " Musical notation system".)

I've seen this clue in The Telegraph.

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