Juan García Castillejo wrote in 1944 'La telegrafía rápida: el triteclado y la música eléctrica' (Fast telegraphy, trikeyboard, and electric music). You can read the gist of it at https://nathanjohnthompson.wordpress.com/2014/07/09/la-teleg...
Here's the book in Spanish https://archive.org/details/latelegrafiarapida.eltritecladoy... and this is a homage to his work in 2013 https://www.youtube.com/watch?v=jFZk6WrbOKw