In Frida, the approach I took scoring the music is that of melodic intimacy (scoring with melodies or tunes as opposed to motific fragments). To achieve additional intimacy I choose a small ensemble of acoustic instruments: the small Mexican guitar (Vihuela), standard classical guitar, Mexican bass guitar (guitarron), accordion, Mexican harp, marimba, and glass armonica (a Benjamin Franklin invention). I found that the guitars provided the full range of lyricism and percussion I needed.
Mexican music cannot be generalized, it varies greatly from one region to the next, but in its folkloric music there is a certain harmonic fingerprint, the use of consecutive thirds and a proud avoidance of over-complex harmonies. I found that if I adhered to this essential harmonic signature, and stayed very honest with my melodies, the movie invited me in. - Elliot Goldenthal