I've received what are supposed to be music notation files with the extension
dds. I'm familiar with
sib etc., but have never seen these. The person who wrote them is not with us anymore, and their heirs, which are not musicians, have sent these to me. It's very possible they were written decades ago.
I tried to find mentions of this format in a relevant context, but could not. Does anyone know what program opens them or how to convert them to a modern format or
midi so that I can open them in Finale or Sibelius?