[Zubersoft]

Yes, the extension matters a great deal. MobileSheetsPro will recognize cho, pro, chordpro, chopro and crd all as valid chord pro file extensions. A text file (.txt) will be treated as such, and will not process any chord pro keywords. This is by design so that users can import text files with chords and different processing will be used to try to distinguish chord lines from lyrics lines. 

Mike