Combination pistons are used to make rapid stop changes from the console on organs with electric stop action. Toe studs are pistons that can be operated by the feet, which change either the pedal stops or the entire organ. In some organs, a "pedalboard check" mechanism serves as a safety catch, to shut off the pedalboard keys. The mechanism prevents accidental foot contact with the pedalboard from sounding notes in a section written only for the upper manuals. The works of Dutch composer, organist, and pedagogue Jan Pieterszoon Sweelinck (1562–1621) contain the earliest example of an independent part for the pedal, rather than a sustained bass drone. His work straddled the end of the Renaissance and beginning of the Baroque eras, and he helped establish the north German organ tradition. Dieterich Buxtehude (1637–1707), who was the most renowned composer of his time, was famous for his "...virtuosity and innovation at the pedal board." The young Johann Sebastian Bach was influenced by Buxtehude, who used the pedal board "as a full-fledged keyboard and devot[ed] virtuoso passages to it." J.S. Bach used the pedal to perform the melody in works such as his setting of the Christmas hymn, In Dulci Jubilo, in which the main theme in the tenor voice is played in the pedal on a higher-pitched stop. Bach also wrote compositions that use the pedal for dramatic virtuoso displays of scales and figurated passage-work in preludes, toccatas, fantasias and fugues. There are a small number of organ compositions that are written solely for the pedal keyboard. English organist and composer George Thalben-Ball (1896–1987) wrote a piece entitled “Variations on a Theme by Paganini” for pedal keyboard. Based on Paganini's “Caprice No. 24”, a virtuoso work for solo violin, it includes pedal glissandi, leaps from one end of the pedalboard to the other, and four-note chords. Firmin Swinnen (1885–1972) was a Belgian organist who became famous in the US in the 1920s for his theater organ improvisations during silent films. Swinnen wrote a pedal cadenza for an arrangement of Widor's "Fifth Symphony". The cadenza was published separately by "The American Organist".