olsner / synsedizer

5-note polyphonic synthesizer in sed

The Synsedizer

Synsedizer takes as input a simple command language describing a musical sequence and outputs a synsedized .au stream on stdout.

Synsedizer probably requires GNU sed as it uses some GNU extensions.

Usage

Two monophonic example inputs are provided, Twinkle Twinkle Little Star and a short sequence of rising notes:

./synsedizer samples/twinkle.txt | aplay
./synsedizer samples/scale.txt | aplay

To demonstrate polyphony, there's also a version of Bad Apple:

./synsedizer samples/bad-apple.txt | aplay

Check the samples/ directory for additional sample inputs.

Using too much polyphony or a too high sample rate may make synsedizer slower than real time, but you can also pipe the output to a file ahead of time and play it with aplay (or your favorite media player) afterwards.

For example, on a less reasonable platform where you need to launch sed explicitly because the hashbang line doesn't work, you might do something like:

sed -rnf ./synsedizer samples/bad-apple.txt > bad-apple.au
start bad-apple.au

Command language

Most commands take a cycle count in number of samples, corresponding to some frequency (or time delay) depending on the sample rate of the output as specified by the r command at the start of the file.

• r R: emit a .au header for a sample rate of R (decimal, Hz).

  Recognized sample rates are 8000, 16000 and 44100Hz.

  It's strongly recommended that this be the first non-comment/blank line of the file, although synsedizer can also be used to output raw samples without a header. In this case, you may need to manually specify the sample format as signed 16-bit big-endian in your player.

• s N: Sleeps for N cycles while outputting synsedized samples before reading the next command from the input.

  For example, s 8000 with a 8kHz sample rate will sleep for 1 second. The sleep command determines the note and rest lengths by spacing out the note on and off commands.

• [abcde] N: "note on" command for one of the five allowed notes a through e. Enables output of the note and sets its wavelength to N cycles. The note will continue sounding until stopped with the corresponding note off command. Use the s command to control note duration.

• [ABCDE]: "note off" command for the corresponding note

• P[tag]: print the internal synsedizer state on stderr for debugging along with the original command (including the optional tag).

License

Synsedizer is available under the MIT license.