If you like using/hearing the instruments used in a Symphony Orchestra you might like to take a look at this new FREE resource recently released by Orchestral Instruments called the Berlin Free Orchestra. It uses the free SINE player and can be driven by a midi source such as Sonic Pi. You can play the output direct, or feed it back into sonic pi as an audio feed. Articulations for the instruments are included and by selected using keyswitches or midi_cc or can be linked dynamically to velocity selection. There are several excellent videsos on the Samples and also on using the Player which can be used directly or as a plugin for a daw like Live or Logic.
Check out the videos here.
or go straight to download here
The player also has several other free library sources of other instruments.