Lambda the Ultimate

The area of computer music has been designing systems for aiding music composition and performance for over 40 years now. The developers have not been much influenced by mainstream programming fads, but have been driven mainly by the needs of composers and performers. Current systems keep the principal original metaphor, the patchboard: a collection of live modules ("patches") connected by cables and easily inspected and modified on the fly. This metaphor has full GUI support and is extended with interactive visual tools for abstraction and exploration, such as the maquette. The language semantics are based on deterministic concurrency, with controlled use of nondeterminism and state.

Current systems are full-fledged programming platforms with visual dataflow languages. Two examples among many are the Max/MSP platform for controlling and generating music performances in real time and the OpenMusic design studio for composers. Max/MSP has two visual dataflow languages: one for control and one for real-time waveform generation. OpenMusic has a dataflow language controlled interactively with many tools for composers.

These systems are actually general-purpose programming platforms. They show that visual dataflow can be made both practical and scalable. In my view, this is one promising direction for the future of programming.

This is kind of obscure. In the "A Tutorial on (Co)Algebras and (Co)Induction" we find the remark (page 28):

If A has more than two elements, then conc(x, y) /= conc(y, x), because they give rise to different observations...

Why is it "more than two" instead of "two or more"?