[sciurius]

I assume you mean this text format:

Code:

      D          G    D
Swing low, sweet chariot,

In the case I have at hand the files are real ChordPro files, there's just some tool (GuitarTapp?) that shares them with extension .txt.

I think you may safely assume a .txt file to contain ChordPro content when it starts with {title...} or {new_song} and then rename it during import.