How many letters does the top answer for “(music) a gradual increase in loudness” have?

The most common answer is crescendo (9 letters).

Crossword clue: (music) a gradual increase in loudness

1 answer found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

crescendo 9 letters wn-def

(music) a gradual increase in loudness

(music) a gradual decrease in loudness 60% similar → decrescendo, diminuendo