Hi Peter --
Thanks very much for the reply, but I don't think that's it. All the missing CDs were identified by the CDDB when I ripped them. I was surprised it knew "Germ-Free Adolescents: The X-Ray Spex Anthology" but it did! Sonos is not finding these artists ripped yesterday, filed under letters W-Y (I don't have any Zs): Roy Wood, Yardbirds, Young Fresh Fellows, Neil Young, X-Ray Spex, Yo La Tengo. Oddly, Sonos does find the several Dwight Yoakam discs I ripped during this session.
I'll get mp3tag and see if that helps. Thanks again.