Violin, Viola,Cello background noise

Nose hair.

I don't think it is dither. Dither is only toggling of the least significant bit, which, with normal gain, is not audible, and would be a pure tone, not a "shushing" sound.

Even with a digital master recording some analog amplification of the microphone is involved, and might contribute some noise. More likely, the analog stages of your digital source may be noisy.

Tilghman: Don't have that one--any from Hyperion or Bis that might exhibit the sound? I might have some of those with chamber groups. This is interesting to me, I might go out and buy this disc (I'd like the music, anyway) just to hear what you're talking about.

I give my second vote to RCprince. I actually own a CD player with adjustable dither. I ran from the highest setting to the "no dither" setting. While the sound signature of the music changed slightly, there is no noticeable noise per se.

But on some chamber recordings there is a slight sound I would also attibute to the bows or something happening non musical with the instruments. I can also hear the clicking of the valves on the wind instruments.

I'm fairly certain the sound is inherent in the recording. It occurs immediately following a note from a "bowed" instrument, and is most noticeable in the quietest passages. The strength of the sound varies greatly from one recording to another, but is very common. I have never noticed the sound in any recording of "non-bowed" instruments. I would like to think the sound is generated by the instruments, but it does not quite resemble any sound I have noticed at a live performance. The idea of the sound being an artifact of "close miking" seems possible. I suppose I've become slightly fixated on the issue because I have spent so much effort , to no avail, tracking down the sound within my stereo. I think I'll bring a couple of CDs to my local HiFi shop to confirm that its not in my head...

Thanks to the group for the input...Tilghman