If you like it old school, you'll want to check out Gleetchplug's Berna, a new virtual studio for Mac OS X that recreates an academic electronic music studio.
Here's what Gleetchplug has to say about Berna:
Berna is a software simulation of a late 1950s electroacoustic music studio. Oscillators, filters, modulators, tape recorders, mixers, are all packed in a easy-to-use interface with historical accuracy.
Explore serial, concrete and tape music or create strange new sonic worlds with instruments inspired by the greatest studios of the early days of electronic music.
Between the 1950s and the mid 1960s, long before Robert Moog and Wendy Carlos injected electronics into pop-music (with a few exceptions like the Barrons and Raymond Scott), electroacoustic music was pioneered by european radio laboratories and US universities. Composing with tapes and electronics was a serious painstaking and expensive affair, prerogative of a restricted elite of contemporary music composers and adventurous sound engineers.
Pricing and Availability
Berna is available now and retails for 10.69€.