From Longman Dictionary of Contemporary Englishsheet musicˈsheet ˌmusic noun [uncountable] 
APMmusic that is printed on single sheets and not fastened together inside a cover
APMmusic that is printed on single sheets and not fastened together inside a coverExamples from the Corpus
sheet music• Clyde also brought along his saxophone and sheet music.• There is also the possibility of further income for the composer from sales of sheet music.• He repaired to it, deposited three dollars, borrowed a book and some sheet music, and then bought a violin.• Although we did receive some sheet music, we mainly got tapes.• He was subsequently traced and cleared by Oxford police, who knew him as Stephen Smith, a wandering sheet music salesman. 