 Francisco Sanguino was one of the first to experiment with fan-bracing, then came Páges and Panormo—but Torres did not use it, so Panormo and Páges still had more tonal energy spread over overtones, compared to the Torres guitars, which focus tonal energy more in the fundamental (desirable in Spanish music).To solve all guitar intonation problems, or help guitarists use different musical temperaments (or to play microtonal music) it is necessary for the frets on the guitar to be adjustable.Work in this field began in the 19th century, when Thomas Perronet Thompson (1783–1869) wrote a work on the "Enharmonic Guitar", with ideas used by Panormo.