Bosanquet developed classes for musical tunings used mapping pitches in a coordinate arrangement he called a generalized keyboard, contrasting with Henry Ward Poole's and Colin Brown's keyboards which were based on symmetry of key relationships. The keyboard was demonstrated in two instruments loaned permanently to the South Kensington Museum in 1876: a 41⁄2-octave harmonium tuned in 53 equal temperament with 84 keys per octave built by T. A. Jennings in 1872-3, and a 3-octave generalized keyboard organ built in 1875 with 48 notes per octave tuned to Hermann von Helmholtz' approximate just intonation (schismatic temperament) or 36 notes per octave tuned in quarter-comma meantone selected by means of draw stops. In 1877, speculating on papers about Indian śrutis, he relaxed the arrangement to permit mapping 22 equal temperament. He also invented a sensitive polariscope working independent of direction.
In 1890 he retired to Tenerife, spending summers in England. He died at home at Castello Zamorra, Tenerife in 1912.