Misc: what is the name of an organism that lives on or in another?

Questions

- A string group consisting of two violins, viola and 'cello.?

(It.) - Played by instruments.?

- Term describes a song which uses the same music for each verse.?

(Ger.) - A composition, piece.?

(Fr.) - Music designed to improve a specific branch of technique by practice. Chopin and Clementi, however, wrote many of artistic merit.?