A multi-instrumentalist is a musician who plays two or more musical instruments at a professional level of proficiency. Also known as doubling, the practice allows greater ensemble flexibility and more efficient employment of musicians, where a particular instrument may be employed only briefly or sporadically during a performance. Doubling is not uncommon in orchestra (e.g., flutists who double on piccolo) and jazz (saxophone/flute players); double bass players might also perform on electric bass. In music theatre, a pit orchestra's reed players might be required to perform on multiple instruments. Church piano players are often expected to play the church's pipe organ or Hammond organ as well. In popular music it is more common than in classical or jazz for performers to be proficient on instruments not from the same family, for instance to play both guitar and keyboards. Many bluegrass musicians are multi-instrumentalists. Some musicians' unions or associations specify a higher rate of pay for musicians who double on two or more instruments for a performance or recording. Early music The European Piffari, Stadtpfeifer and Waits were multi-instrumentalists, who played trumpet, sackbut, shawm, cornett, recorder and string-instruments. Musicians with an education of a Stadtpfeifer were Gottfried Reiche, Johann Joachim Quantz, Johann Christof Pezel and Sigmund Theophil Staden. Also many European church musicians of the 17th and 18th centuries were multi-instrumentalists, who played several instruments. Georg Philipp Telemann for example played violin, viola da gamba, recorder, flauto traverso, oboe, shawm, sackbut and double bass. Classical music Some famous classical composer-performers could play multiple instruments at a high level, such as Mozart, who was a virtuoso on the keyboard and violin. Music written for symphony orchestra usually calls for a percussion section featuring a number of musicians who might each play a variety of different instruments during a performance. Orchestras will also often, but not always, call for several members of the woodwind section to be multi-instrumentalists. This is sometimes referred to as doubling. Typically, for example, one flute player in the orchestra will switch to playing the piccolo or alto flute when called to by the score. Similarly, clarinet players may double on bass clarinet, oboe players on cor anglais, and bassoon players on contrabassoon. Trumpet players may switch to piccolo trumpet for certain Baroque literature, and first trombone players may switch to alto trombone. Bass trombone players are sometimes required to double on contrabass trombone, most notably in Wagner's Der