Wednesday, June 8, 2011

Playing the loop

After watching the video above, I started fooling around with this technique in Ableton. Using recordings I made with Big Band Caravane in 2006 as a starting point, I isolated the beginning of phrases and swells instead of drum sounds as Thavius Beck does in the video.

Here are some results:

You gotta try1

Livelooping application
As fun as it was to pretend to be a dj for a couple afternoons, my musical path does not lie in that direction. I quickly began to consider ways I could apply this technique to a live recording in a given performance. Now, I know there are easy ways of doing this with the full version of Live (clip to midi controlled rack instrument), but I’ve been reticent to upgrade from my free watered-down version in part because I believe a new version is just around the corner, but mostly because I want to limit the number of software I’m using in performance. So far, I’ve been able to do everything with Bidule and Mobius and I’ve only looked at Ableton to work out performance strategies and to try out ideas I find on the web.

Fortunately, it turns out it is easy enough to tell Mobius to trigger a loop from a certain point. The following script will trigger playback from 4/16th of its length:

!name trigger4
Variable newFrame loopFrames / 16 * 3
move newFrame
I wrote sixteen scripts like the one above, with different values, and assigned each one to a pad on my Trigger Finger using MIDI binding. Once a loop is recorded, pressing a pad triggers playback from one of sixteen positions relative to length. If I have a one bar loop, that’s every 16th note. Four bars will give me a trigger point at every beat.

Here are some results using that approach with a song from my homage to the cookie monster:

No birds remix1

No birds remix2

I’m quite excited about the possibilities this technique highlights. I quickly came up with new and interesting ideas using old ones. I found this process of creating from existing material very much in line with my current interest in collage in comic books and video.

If anything, these new experiments have only further revealed the need for an integrated instrument/controller: the meta-trombone. My current vision is to make those loop points trigger according to what notes I play on the trombone. After recording an initial loop, this would allow me to continue to play a ‘duet’ with myself since every note played would have a double purpose, serving both as musical material and trigger signal.

Technically, the challenge is to interpret the notes I play into MIDI notes. This is a rather complex problem to solve if I ask the computer to determine the note played from any of 30+ possibilities, but it becomes easier if I narrow the options to something more manageable.

One way students at Cornell have tackled this problem in the case of a MIDI trumpet was to split it in two. First, they developed a system to determine which valves were activated. This limited the number of possible notes (8 or so) and they were then able to track the notes being played.

I intend to take a similar approach for my meta-trombone controller. I’ve already had good results tracking the notes I play in 1st position using Bidule and I think I can scale this up to all positions, provided that I can find a way to determine slide position.

Thankfully, I’m not the first person to tackle this problem and I found some interesting experiments online. The first I looked at was Nicolas Collins’ Trombone-Propelled Electronics (and its various incarnations). To track slide position, Collins cleverly used a retractable dog leash to turn the knob on an optical encoder (figure 4 in the pdf). I considered using a similar approach using string potentiometers, but I was unable to find one with a string tension that would not impede playability.

The wireless options I’ve encountered used either optical or ultrasonic sensors. The composer Marco Stroppa’s work "I will not kiss your flag" called for an augmented trombone that would use the slide as a continuous controller to change parameters during performance. The solution adopted was to place a red laser light emitter on the outer slide (the moving part) and a photo-electric diode receiver at the fixed end. However, the article seemed to indicate the reliability of the system could be improved.

Ultrasonic emitter and receiver pairs seem more promising. A study trying to link technical ability and movement efficiency in trombone playing had success with an ultrasonic sensor, noting that the system they developed was lightweight and did not detract from playing. They placed an emitter/receiver paired unit at the end of outer slide and (from what I can tell) they measured the distance the sound travelled from the emitter to the receiver, bouncing off the player on its way.

Neal Farwell developed multiple technical systems to adapt the trombone for the electro-acoustic performance of his Rouse. One of them, called the uSlide, is a pair of ultrasonic emitter and receiver that tracks slide position. His approach is different from the one above, since he put the emitter on the outer slide and kept the receiver fixed near the mouthpiece. This seems a more robust approach, but I’ll have to try things out.

Also of interest, the trombone instrument from the Imaginary Marching Band project tracks “slide” position with a ultrasound sensor connected to an arduino. The open-source software developed for the arduino outputs MIDI note information (including pitch bend).

There may be ultrasonic sensors in my immediate future…

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