I compose music using digital signal processing and algorithms within Max/MSP. I particularly like the Spat~ object for positioning the sources of audio channels in 3D space around the listener's head. Pro Tools and Audacity are great for mixing and I use Peak Pro for convolution. SPEAR represents sounds as collections of sinusoidal waves with time varying frequency and amplitude, so it's perfect for finding fascinating sounds within other sounds.
I write software in a variety of programming languages, including Python, Ruby, and Clojure. Processing from the MIT Media Lab is ideal for quickly getting interactive audiovisual projects running.