A trill is a melodic embellishment produced by rapidly alternating two notes a step or semitone apart. The effect closely resembles the way that speakers of certain languages roll their R’s (always with great gusto), which is also called a trill (or to linguists, “trilled rhotics”).
The bottom note of a trill is always the “main” note, making the top note the “embellishing” note.
In melodic figuration, the name “Trill” refers to a slow-motion version of the ornamental action of alternating two notes.
Some birdsong contains trills. The following description comes from the opening page of Eight Cousins by Louisa May Alcott. Notice how the variety of melodic “figures” she mentions parallels the way trills incorporate themselves into human melodies.
Before she had time to squeeze out a single tear a sound broke the stillness, making her prick up her ears. It was only the soft twitter of a bird, but it seemed to be a peculiarly gifted bird, for while she listened the soft twitter changed to a lively whistle, then a trill, a coo, a chirp, and ended in a musical mixture of all the notes, as if the bird burst out laughing.
synonyms: warble, oscillate, alternate, shake,