Polyphone (Free, cross-platform).
"The high notes squeak like a dying cat." Solution: That is actually realistic (violins squeak when played badly), but for production, lower the "Key tracking to filter" in your player, or apply a gentle low-pass filter above 8kHz. violin sf2 patched
The difference between an amateur violin track and a professional one is often not the price of the library, but the attention to the patch. A "patched" violin has been kissed by a sound designer who cared about the loop, the envelope, and the velocity curve. That care translates directly into your music. Polyphone (Free, cross-platform)