During the Baroque era, keyboard music played on the harpsichord and pipe organ became increasingly popular, and the violin family of stringed instruments took the form generally seen today. Opera as a staged musical drama began to differentiate itself from earlier musical and dramatic forms, and vocal forms like the cantata and oratorio became more common. Vocalists began adding embellishments to melodies. Instrumental ensembles began to distinguish and standardize by size, giving rise to the early orchestra for larger ensembles, with chamber music being written for smaller groups of instruments where parts are played by individual (instead of massed) instruments. The concerto as a vehicle for solo performance accompanied by an orchestra became widespread, although the relationship between soloist and orchestra was relatively simple.