The term 'songbird sound' can be summarized by two crossword solutions: TRILL (5 letters) and CHIRP (5 letters). A TRILL is a rapid alternation of two or more notes, usually on the same pitch. It is often used in classical music and bird songs. A CHIRP is a short, high-pitched sound made by a bird. It is usually used to communicate with other birds or to attract a mate. Both trills and chirps are common sounds made by songbirds.