I can confirm that John is right. I went through this very thing.
Removed the decoder from a Kato Kobo custom, installed it in a Kato RDC. Went to load a LS5 sound file for an RDC only to find that the Kobo had used an older Select, and the file was a no-go. And of course there was no RDC soundtrack in the Select files. Had to settle for some random file that just had some appeal of some sort.