reference recordings

If your question is based on sound quality, just about any of them. Hard to go wrong. The HDCD versions might be best if you have a unit which can decode them. If you are talking about performance quality, which performances are you interested in?

either jazz or classical

You could try Dick Hyman "Swing is Here" I think it sounds pretty good.

I only have it on vinyl, but I really like the Kronos Quartet - "In Formation" RR-9. I have quite a few others, but frankly, I'm not nearly as crazy about most RR's as some people - either from a recording or performance standpoint.

The one's on Arthur Salvatore's (who's opinions I generally find accurate) list are:

ARNOLD-OVERTURES-ARNOLD/LPO-REFERENCE RECORDINGS RR-48

EBONY CONCERTO-YEH/DEPAUL UNIV. WIND ENSEMBLES-REFERENCE RECORDINGS RR-55

FIESTA (REED/GOULD/NIXON/WILLIAMS/PERKINS)-DUNN-REFERENCE RECORDINGS RR-38

WEBER/BRAHMS-CLARINET QUINTETS-EDDIE DANIELS-REFERENCE RECORDINGS RR-40

I like the non-HDCD discs from RR just as much due to the clarity of the recordings-some of the best discs i've ever heard (the Helicon Ensemble disc playing bach/baroque is clear as a bell). HDCD is fantastic though- i like Trittico- dallas wind symphony with lots of percussion and brass. the problem with HDCD is the huge dynamic range- 1st you have to turn up the volume way higher than with regular cd's because of the hdcd filter, but then you have to keep your remote handy in case your speakers can't handle the really loud parts. i hear they are coming out with more titles now, which is very good news.