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
The problem I have is that it varies from recording to recording. So there's really no way to balance your system to make everything sound good, unless you roll the highs off so much that other instruments start to sound dead.

When I come across a recording with screechy strings, I typically grit my teeth and listen to something else instead.
There is one thing no one mentioned. That is the type of violin and strings used in that recording. That will have a significant effect on what you here (obviously). The recording is part of it, yes, but I can tell you you'll run screaming if I place Dominant's run-of-the-mill strings on my violin versus Pirastro "Olive" Gold strings which are silver/nickel wound over gut and you'll melt in your chair.

The point of my response, while the OP is geared toward the recording, it still failed to recognize the instruments themselves. Some people really just play on crappy strings. It may have been the recording of the century too but it still won't sound sweet.
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.