What makes strings sound "sweet"?


I have always wondered about this. If you listen to many recordings of bowed string instruments, then you know that the upper registers can sometimes have a sweet tone. I define this by what it is not - edgy, brittle, dry and rough sounding. It is smooth and inviting. I used to assume this was due to rolled off highs or an emphasized midrange, but I am not so sure. It varies by recording, or course, but I have often wondered what, in the recording or reproduction process, causes strings to either sound brittle or sweet. Is it the acoustic of the original recording venue? A frequency balance issue? I would love to hear from those who might know. Thanks!
bondmanp
I think it is due to tone woods and the type of varnish they use and the strings and the bow and the player too.
How to get to Carnege Hall - Practice!
Of course woods and varnish have a role as with the overall size of the instrument as well. Horsehair bow vs. synthetic. Type of rosin used, ivory frog vs. plastic/bone frog, type of wood in the bow, etc..etc. The player is probably one of the more important keys. A good player can help a not-so-great instrument sound just a little better.

Citing all of this I think it is nearly impossible to obtain a perfect recording, unless you are Maxim Vengerov or Hogan. Then you are just perfect whether it be an iPhone recording or professional. ;-)
Good responses, but if we already have a well-recorded section (either live or a good VI like Vienna Symphonic or Hollywood Strings), how do we get a sweet Montavoni or Mancini sound? I *think* this is an EQ question and I am hoping for guidance.

Regarding the various harmonics in the series, I am impressed by the knowledge here, put I don’t know of a simple technique to alter harmonic content selectively.

A practical answer would be greatly appreciated.
Example of what I mean: I’m sure varnish is something of a factor, but I don’t think we can control that, and I doubt producers recording strong sections look into that.