A CODA is a concluding section of a piece of music, usually signifying the end. A rondo is a musical form consisting of a recurring theme alternating with different episodes. A CHORD is a combination of three or more notes played together. SHEET music is a written representation of music, usually on paper. A NOTE is a single sound or pitch. An opus is a musical work, often numbered to indicate the order of a composer's works. An etude is a short composition, usually for a solo instrument, designed to improve a particular skill. Together, these terms refer to various types of pieces of music.