There have historically been three distinct classes of electroacoustic music instruments or systems: 
Musique concrete tape based studios  Modular Analog synthesizers Moog, Buchla, ARP and EMS.  SoftWare-based Sound Synthesis systems(swss). Csound, Music 4C, Common Lisp,  MusicMode,  SoundKit,  Next... 
Csound was developed during the late 1960's by Barry Vercoe a the University of Princeton.
Written entirely in C. Csound is a very portable language and can operate on UNIX workstations, IBM PC compatible, atari and Apple Macintosh. 

Csound uses a mix of assembly language and Fortran as its programming language model but should not be discouraged if one has no programming experience. Tutorials and examples are available and make learning and crating with Csound very rewarding despite a learning curve.

The Csound community is open to sharing new developments and the software is continually updated and modified for the above mentioned platforms.

Graphic user interfaces have been developed as shareware and software for creating scores have also been made available as shareware.

Try the following site for collecting the software and manual: