The most common and most likely answer to this crossword clue is the 8 letter word WARBLING
I've seen this crossword clue in The Sunday Telegraph
W
A
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Buddy explains!

The straight part
We know that "Making musical sounds" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case making musical sounds = warbling.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does WARBLING mean?
WARBLING verb- To modulate a tone's frequency.
- To sing like a bird, especially with trills.
- To cause to quaver or vibrate.
- To be quavered or modulated; to be uttered melodiously.
- A sound that warbles.