How many letters does the top answer for “composed or performed by a single voice or instrument” have?

The most common answer is solo (4 letters).

Crossword clue: composed or performed by a single voice or instrument

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

solo 4 letters wn-def

any activity that is performed alone without assistance