The examples here have all been realized using Pure Data (Pd), and to use and understand them you will have to learn at least something about Pd itself. Pd is an environment for quickly assembling computer music applications, primarily intended for live music performances involving computers. Pd's utility extends to graphical and other media, although here we'll focus on Pd's audio capabilities.
Several other patchable audio DSP environments exist besides Pd. The most widely used one is certainly Barry Vercoe's Csound, which differs from Pd in being text-based-not GUI based--which is an advantage in some respects and a disadvantage in others. Csound is better adapted than Pd for batch processing and it handles polyphony much better than Pd does. On the other hand, Pd has a better developed real-time control structure than Csound. More on Csound can be found in ([Bou00]).
Another alternative in wide use is James McCartney's SuperCollider, which is also more text oriented than Pd, but like Pd is explicitly designed for real-time use. SuperCollider has powerful linguistic constructs which make it more useful than Csound as a programming language. Another major advantage is that SuperCollider's audio processing primitives are heavily optimized for the processor family it runs on (MIPS), making it perhaps twice as efficient as Pd or Csound. At this writing SuperCollider has the disadvantage that it is available only for Macintosh computers (whereas Pd and Csound both run on a variety of operating systems.)
Finally, Pd has a widely-used relative, Cycling74's commercial program Max/MSP (the others named here are all open source). Both beginners and system managers running multi-user, multi-purpose computer labs will find Max/MSP better supported and documented than Pd. It's possible to take knowledge of Pd and use it on Max/MSP and vice versa, and even to port patches from one to the other, but they aren't truly compatible.