Other Steely Dan tunes and albums sound fine. Agreed, these are reference discs and that's why I'm raising the issue. Because if anything should sound good, these do.
@gosta I suspect that Gaucho (and possibly Nightfly) crossed a line (accidentally) as the industry moved to digital. My guess is that this was recognized and corrected. There is a comment from their Scheiner or Fagen down below on this thread (around the time of Morph's release) where they go back to analog recording. I've noticed that the brightness I'm referring to is NOT there on Kamakiriad, Sunken Condos, or Becker's albums. And again, as decooney and others point out, it could be the mastering or release for one medium or another that's at fault.