Awesome

This is Pytebeat, a piece of software I wrote for doing livecoding bytebeat performances --- that is, writing tiny programs that generate music while the program is running, in front of an audience.

I, the copyright holder of Pytebeat, hereby release it into the public domain. This applies worldwide.

In case this is not legally possible, I grant any entity the right to use this work for any purpose, without any conditions, unless such conditions are required by law.

Prerequisites

If one of these commands works for you, you can probably run it with no trouble:

sudo apt-get install alsa-oss python-numpy python-pygame

or

sudo apt-get install alsa-oss python-numeric python-pygame

My netbook is running a pretty obsolete version of Linux, so this uses the obsolete interface /dev/dsp, the OSS device interface that can be implemented by the aoss command from the alsa-oss package.

It also uses PyGame, the Python interface to SDL.

I haven’t figured out how to call Core Audio from Python on MacOS X yet. (I figure it’s probably possible with PyObjC, but OS X doesn’t ship with PyGame or SDL anyway.)

How to use it

./pytebeat.py

or if that craps out complaining about /dev/dsp, try

aoss ./pytebeat.py

Then edit the C expression in blue using your cursor keys and stuff. It ought to make sound right away. If not, check to see if you’re muted or something.

Pressing any mouse button should exit right away.

The formula editor

I wrote a quick-and-dirty text edit field, with the special feature that the up and down arrows increment and decrement the number your cursor is on. Beyond that, it supports left and right arrow keys with the usual hold-shift-to-select-for-deletion technique of modern GUIs. Home and End go to the beginning or end of the field, and of course backspace deletes. The Alt key multiplies your movements or deletions by 4.

There’s no scrolling, so keep your formula short, or you won’t be able to see what you’re doing.

The formula language

Pytebeat interprets an expression in a common subset of C and JS. (Yes, that means I wrote a C-subset interpreter in Python. Hush, you; it seemed like a good idea at the time. It uses a SIMD evaluation approach with Numeric, so it isn’t a significant performance bottleneck. And as a pastime it sure beats watching TV or drinking.)

The supported expression subset includes assignment and the comma operator, so you can write a comma-separated series of assignments. The other supported operators are |, ^, &, <<, >>, + (binary), - (unary and binary), *, /, %, ==, !=, <, >, <=, >=, &&, and ||. The only significant bytebeat operators omitted are ?:, >>>, and [].

Precedence is as in C, unless I fucked it up.

The rest of the expression language consists of numbers (decimal only so far) and variables.

However, that’s not all there is to the story! Several of the operators have weird incompatibilities.

Division, of course, behaves differently between C and JS. Pytebeat produces integer results, as in C, but doesn’t crash on division by zero, as in JS. Both / and % simply return 1 on division by zero. (Because division-by-zero errors are incompatible with livecoding.)

The && and || operators ought to be short-circuiting, but they are not. SIMD short-circuiting is difficult.

* was giving me ArithmeticError exceptions in Numeric. So I “fixed” it to only use the low 15 bits of each multiplicand. That means you’ll get wrong answers as soon as either of your multiplicands goes over 32767. I think at least the low 15 bits of the answer will be correct, though, so for bytebeat purposes, you’ll probably never notice. I’d be fabulously happy if you can suggest a better approach to this problem. You’d think that Numeric would have a truncating-multiply function somewhere, but if so, I can’t find it.

Background

I wrote it for a performance I gave at the u-micron event at the bar La Cigale in Buenos Aires on the night of May 5th, 2012. I wasn’t on the program, but I asked the organizer on Facebook if she’d like me to show off some bytebeat there, and she agreed, so at the end of the night, I improvised bytebeat for about seven minutes. I uploaded the result, but without nightclub levels of bass, it doesn’t really sound the same.

It’s not the only program you can use for livecoding bytebeat. I’ve used the Entropedia Flash applet too, and there’s also an iOS app called GlitchMachine that’s suitable for livecoding. And I’ve heard that GlitchEd may be suitable for livecoding too.