• Mathematics of Sound
  • Musimathics by Gareth Loy (an excellent text, but amazingly there is nothing on stretch and inharmonicity)

Interesting papers in the professional literature:


The Six Degrees of Tonality, pianist: Enid Katahn (with piano prep and notes by Ed Foote).
Beethoven in the Temperaments: Historic Tunings on the Modern Concert Grand, pianist Enid Katahn (with Ed Foote).
Beethoven's Last Piano Sonatas, pianist Penelope Crawford (playing a fortepiano in historic (similar to the Valotti) temperament).