As an English violist and theoretician Simpson was important for his work entitled "The Division-violist" and "Practical Musick." He was an excellent teacher and skilled performer. Compositions by Simpson for the viola included suites, divisions and fantasias which were set for both solo instrument and consort alike. The "Division" includes instructions on playing the viola as well as information concerning the instrument. Simpson's "A Compendium of Practical Musick" addressed basic information concerning pitch and time signatures, the use of intervals and cadences as well as progressions and the proper handling of dissonances in composition. In the "Compendium" Simpson also discussed the appropriate treatment of scales, counterpoint, imitation and formal musical structures. ~ Keith Johnson, All Music Guide