Steely violins are caused by bad mic placement. Violins radiate different frequency bands in different directions. For that reason, if you place a microphone right above a string section, it will sound shrill and steely. One solution is to try to equalize the shrillness out of the feed. A better one is to mike the orchestra properly, with a stereo pair flown above the front of the stage.
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!