The term 'SINGER's Instrument' can be broken down into two crossword solutions: VOICE (5 letters) and VOCALCORDS (10 letters). VOICE is the sound produced by a SINGER, which is created by air passing through the vocal cords. The vocal cords are two folds of mucous membrane located in the larynx, which vibrate to produce sound when air passes through them. Together, these two solutions form the instrument of a SINGER, which is their VOICE.