The most common and most likely answer to this crossword clue is the 9 letter word FREQUENCY
I've seen this crossword clue in The Guardian
F
R
E
Q
U
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N
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Y
More clues leading to the result FREQUENCY
Buddy explains!
The straight part
We know that "How often/might it be modulated" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case how often/might it be modulated = frequency.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 FREQUENCY mean?
FREQUENCY noun- The rate of occurrence of anything; the relationship between incidence and time period.
- The property of occurring often rather than infrequently.
- The quotient of the number of times n a periodic phenomenon occurs over the time t in which it occurs: f = n / t.
- Number of times an event occurred in an experiment (absolute frequency)