The OED was never meant as exhaustive…the c. 1250 reference for M-u-s-i-c is incorrect, as the OED entry reveals! Ironically, neither the Grove Dictionary of Music nor the Grove Dictionary of Art reveal the origin of M-u-s-i-c! No letters…of composers extant?! Not even a word from the Editior - or Archivist! - of the MED, or Middle English Dictionary?! The word from The Cecil Council is The High Cecil answers one inquiry at a time, and perhaps a genius Philologist on the message board will reply…Well?!
…etymology!
…Editor!
…Cecil, your message board word processor microchips are some of the worst!
Welcome to the SDMB. Good luck with getting this question answered… however:
To be quite honest, I have no idea what you’re talking about. Please rephrase your entire OP, perhaps quoting directly from the various dictionaries you mentioned, and then explain exactly what question you want us to answer. Thank you.
Calm down,and let’s look at this.
The 1989 version of the OED said c 1250 for the cite from The Story of Genesis and Exodus
[How *thoughtless* of the writers of that tome to not put a publication date on the flyleaf] :rolleyes:
The December, 2003 draft edition says
If I read this right, it was before 1325, but about 1250. Hey, give 'em a break. They’re doing the best they can. It’s a work in progress. As Cecil would observe, it’s taking longer than we thought. . 
If you have access to their on-line version, go to the etymology button and you see
Then, they take it back to the original Greek, which I’m not gonna try to reproduce here. Lazy.
Then this–
Cf. Old Occitan muzica (mid 13th cent.; Occitan mesico, musico), Catalan música, Spanish música (c1250), Italian musica (c1250), Portuguese música (14th cent.), and also Middle Dutch muske (Dutch muziek), Middle Low German msike, mseke, Old High German musica (Middle High German mseke, msic, early modern German music, German Musik), Swedish musica (1536), musik (1579 in form musich)).
Sorry to not take the time to italicize, etc.
Does any of this help?