Siren is typically used in consort with a number of other packages; for more information, see the links below

CSL--the CREATE Signal Library: a C++ framework for building OSC-controllable synthesis/processing servers
   http://create.ucsb.edu/CSL

SuperCollider: an efficitne synthesis and processing language very similar to Smalltalk
   http://create.ucsb.edu/CSL

CRAM--the CREATE Real-time Applications Manager: a tool for describing and managing complex distributed real-time software systems
   http://create.ucsb.edu/CRAM

Occam: An OSC=-to-MIDI translator
   http://www.mat.ucsb.edu/~c.ramakr/illposed/occam.html