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Data-Driven DJ Track 3: Air Play

You can listen to this track and read the full description here.

Software Required

All software required for making this song from scratch is free and open-source

  • ChucK - a programming language for real-time sound synthesis and music creation
  • Python - I am running version 2.7.3
  • Processing - optional, for supporting visualization


Select And Process Data

  1. Download .csv files from the U.S Embassy Beijing Air Quality Monitor and place them in the folder data/raw. In my piece, I selected the last three .csv files for years 2012, 2013, and 2014, but you can select any number of files.
  2. Run python preprocess_data.py from the command line in this directory
  3. This generates data/pm25_readings.csv which will be used to generate your song later steps

Prepare Sound And Configure Files

  1. Create a tab-delimited instruments.csv file based on instruments.csv.sample file and place in folder /data
  • PM2.5 Min and PM2.5 Max is the pm2.5 value range the instrument is allowed to play in. This value is normalized between 0 and 1.
    • Residue Min and Residue Max is the pm2.5 residue range the instrument is allowed to play in. This value is normalized between 0 and 1.
  • File is the filename of the instruments sound file
  • From Gain and To Gain is the volume range this instrument can oscillate between. A value of 0 is silent.
  • From Tempo and To Tempo is the tempo range this instrument can oscillate bewteen. A value of 1 is standard BPM, 2 is twice as fast, 0.5 is twice as slow.
  • Tempo Offset is the offset as a percentage of the instruments tempo. For example if an instrument's tempo is 1 and the tempo offset is 0.5, the instrument will on the half beat.
  • Interval Phase, Interval, Interval Offset control at what intervals the instruments can play. For example, if interval phase is 16, interval is 2, and interval offset is 1, every 16 beats, the instrument can play on the 2nd half of the beats (8-16).
  • Active essentially activates or deactivates an instrument
  1. Prepare all your sound files and place in folder /instruments. All files should be in .wav format. For best results, I'd recommend using very short clips (< 500ms).

Configure The Scripts

  1. Python script: smog.py
  • BPM is the song's beats per minute.
  • READINGS_PER_BEAT is the amount of pm2.5 readings per beat. In general, the higher this number, the shorter the song.
  • DIVISIONS_PER_BEAT is how the beats are divided. For example, a value of 4 would create quarter-notes as the smallest unit, 8 would create eighth-notes, etc.
  1. ChucK script: smog.ck
  • padding is the amount of milliseconds before and after the song.
  • instrument_buffers is the number of buffers each instrument has. If you hear clipping in your song, you will want to increase this number.
    • start is which millisecond you would like the song to start on. Useful for debugging a particular part of the song.

Generating The Song

  1. Run python smog.py in the project's directory. This will generate two files that ChucK will use:
  • data/ck_instruments.csv: A manifest of instrument files
  • data/ck_sequence.csv: A sequence of instruments
  1. Open up smog.ck in ChucK. You can either export the song to .ogg/.wav or start your VM and add a new shred

Generating The Visualization

  1. Open visualization/visualization.pde in Processing. This script generates a visualization based on the pm2.5 data.
  • this script uses data (pm25_data.json) generated from previous python script
  • set boolean captureFrames = true; to output frames to output folder
  • run script, this will generate frames at the framerate (fps) in the configuration