Strings shouldn't sound overly aggressive, but they also shouldn't sound too sweet. Depending upon the instrument and the player it can be very appropriate to have a little bite or even rasp to the sound. The choice of microphone and its placement are the biggest factors in string recorded sound quality.
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!