Didn't Janaček at one point write a newspaper column one of whose features was musical transcriptions of snippets of speech that he found particularly interesting? I think I read that somewhere. His short-fusedness certainly shows itself in his structural thinking, where thematic material is very seldom carried over, for example, from one scene of an opera to another.

Martinů's music seems to me more rooted in Dvořak and Smetana, as well as the quasi-baroque textures he picked up when living in Paris when neoclassicism was the height of musical fashion, and later on Bartók. So any direct connection his music might have to Czech folk music (and therefore speech-rhythms) is at least at second-hand.

I see the second volume of Hyperion's Martinů violin/orchestra music is out next month, containing the duo concerto for violin and piano. This is really not to be missed.