PLOrk fall2006/Works/Smacking Music

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Smacking Music

  • composer: Rebecca Fiebrink
  • duration: 1' + (adjustable)
  • software used: OS X
  • hardware used: 5 PowerBooks with the built-in sudden motion sensor (SMS) in working order

Program Notes

This piece encourages the performer and audience to reconsider the definition of "laptop music." Smacking Music explores the use of the laptop as an acoustic instrument: all sounds in this piece result from hitting, smacking, slapping, banging, or otherwise physically abusing the laptop itself. The digital/electronic capabilities of the laptop are nevertheless utilized by means of the internal motion sensor, which allows the machine to output visual effects via its screen in response to performer smacks.

This piece is not only a bastardization of traditional laptop performance, but also of Steve Reich's well-known piece for two human clappers. In Smacking Music, the "score" is simply a modified version of Clapping Music, adapted for 5 smackers and adjusted in length and tempo at whim.

Laptop Instructions

To compile

  • In Terminal, go to directory containing smack-sense.c, type "make" at command prompt.

To check runtime settings

  • In Terminal, go to directory containing "smack-sense" executable (created by "make" above). Type "./smack-sense" at prompt.
    • If this does not work, you may have to make "smack-sense" executable with the following command: "chmod 755 smack-sense"
  • To adjust the responsiveness of smack sensing program, you may change the sensor polling rate and smack activation threshold using command-line arguments to "smack-sense":
    • "./smack-sense p" will supply a polling period; e.g., use "./smack-sense .5" for half-second polling (2 polls per second)
    • "./smack-sense p t" will supply a polling period and smack threshold; e.g., use "./smack-sense .5 10" for a threshold of 10
      • Lower thresholds are more sensitive.
      • Threshold should probably be between 5 and 25.
      • Default settings are .1 for polling period (10Hz) and 10 for smack threshold.
  • If smacking doesn't work, verify that SMS is turned on, by running "pmset -g" at the command prompt and verifying that "sms" is set to "1".
    • If SMS is not turned on, enable it by running "sudo pmset -a sms 1" at the prompt.


  • files: Makefile, smack-sense.c
  • score: "Clapping Music" by Steve Reich.

Human Instructions


  • Divide into Group 1 and Group 2 (e.g., adjacent performers take different groups)
  • Agree on how many times each measure will be repeated
  • Open Terminal application, and adjust terminal window to take up the full screen.
  • Change the terminal window background and font colors to a satisfying combination. (Open up the Terminal Inspector by "Terminal" -> "Window Settings," then select "Color" in the drop-down box in the Terminal Inspector.)
  • Run "./smack-sense" program at command prompt (adding command line arguments to adjust polling period and threshold if necessary), and verify that smacking results in changes to the screen. If this doesn't work, see "To run" instructions above.
  • Commence Smacking Music
    • Smacking is performed by striking the laptop body or sides with hands or object (e.g., pencil). Each performer can choose their own smacking technique.
    • Group 1 plays part 1 and Group 2 plays part 2, repeating each measure the agreed-upon number of times.