The most common and most likely answer to this crossword clue is the 9 letter word SFORZANDI
S
F
O
R
Z
A
N
D
I
Buddy explains!
The straight part
We know that "Suddenly stressed notes" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case suddenly stressed notes = sforzandi.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 SFORZANDI mean?
SFORZANDI noun- A mark that indicates that a note is to be played with a strong initial attack.
- A passage having this mark.