The term Wavy Lines, in Music is often referred to as Trills (6 letters). A trill is a musical ornament consisting of a rapid alternation between two adjacent notes, usually a semitone or tone apart. It is commonly used in classical music and jazz, and is also found in other genres such as rock and pop. Trills are often used to add expression and emotion to a piece of music, and can be used to create a sense of tension or excitement.