I’ve written before about how great Netflix streaming movies are. The library isn’t spectacular; however, if you’re into documentaries, you can instantly watch a huge selection. I love docs, and over the past couple weeks I’ve seen a few specifically about artists: Rivers and Tides, Scratch, B-Boy Planet, and Touch the Sound.
Scratch is about turntabalism, a musical form where the instruments are record players. While these turntables produce highly unique sounds, they also are capable of mimicking any other instrument depending on the given input (i.e. record). This will instantly remind any computer scientist of universal Turing machines, which are capable of mimicking any other Turing machine. (Turing Machines, first defined by Alan Turing, are the basis of all computation including human intelligence (more about this in future posts)).
A musical instrument which can mimic any other might be called a “universal instrument.” It seems there are 2 categories of universal machines: audio players which can play an arbitrary input (e.g. record players, cd players, mp3 players), and instruments which can change their tones in real-time (e.g. tone generators, synthesizers, computers). Any device which can output arbitrary sine waves in unison can re-create any other instrument due to Fourier decomposition.
Some might debate whether a cd player is really an instrument, but it becomes clear when you realize a musician can manipulate the output through even rudimentary controls (e.g. seeking, volume). A more realistic debate is whether such a player is really a universal instrument, if all of the information is only in the input string. Interestingly, this parallels a similar debate about a disputed univeral Turing machine! Stephen Wolfram offered $25,000 for a proof that this machine was in fact universal. It only has 2 states and 3 symbols and is the simplest possible universal machine, although some have debated whether the universality is only a result of a specific input, which actually encodes the universality, and not the machine itself.