Improvisation was once a normal part of a performer's stock-in-trade. Many of the greatest composer-performers, from Bach to Mozart and Beethoven, were masters of improvisation, but in the 19th century this became a less common part of public performance, although it remained and remains a necessary skill for a church organist, traditionally required to provide a musical accompaniment of varying length to liturgical ritual. In baroque music the realisation of a figured bass, the improvisation of a keyboard part from a given series of chords, was a necessary musical accomplishment, while the improvisatory element in the addition of ornaments to a melodic part remained normal in opera and other kinds of solo performance.