Beam Beats tangible rhythm sequencer: work is in progress!

Beam Beats is an interactive and tangible rhythm sequencer that translates the geometry of beacons on the ground into rhythms and polyrhythms thanks to a rotating laser beam. This experimental MIDI instrument is about investigating self-similarities in polyrhythms, as described in this post.

Update: Here’s the video of a demo at Dorkbot at La Gaité Lyrique in Paris

BeamBeats demo at Dorkbot at la Gaité Lyrique from cyrille martraire on Vimeo.

Before I report more on this project with demos and videos, here are some pictures to illustrate the work currently in progress, thanks to lasercutting techniques in particular:

The brand new laser-cut acrylic structure
The prototype laser head and retro-reflection light sensor
The Arduino to detect the light variations and convert them into MIDI notes
Very early design of beacons each with their own light sensor

This prototype works, here’s a picture of the laser beam rotating:

The revolving laser beam reflected on the wall

And here’s a very short early video (no sound)

Beam Beats – revolving laser beam to detect beacons from cyrille martraire on Vimeo.

I’ve been working on the Arduino source code to add the ability to send MIDI clock in order to sync Beam Beats to other MIDI devices.

Now I mostly need to conclude on the design for the active  beacons(sensors stands) and the passive (retroreflective adhesive stands) beacons, and find out what to play with this sequencer…

Every post on this project:

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Jam Session at home

On a Sunday afternoon, fifteen friends, all non musicians but two amateur musicians, joined the machines set in turn, around 8 at a time, to improvise electro or hip-hop rhythmic grooves. Of course there were food and drinks as well.

The goal was to introduce music making in an attractive way: no pressure, no constraint, no reason to be shy, just have fun!

Don’t be shy

Some arrived saying “no no no I will never sing in the mike”, but ended up doing the mike to record voice loops into the Kaoss Pad… Other spent time to figure out how to play something musical from machines they were touching for the first time. It was amazing how everybody got into it!

Here is a time lapse overview, unfortunately silent:

Jam Session at home with friends from cyrille martraire on Vimeo.

The machines setup

The machine set was primarily composed of an Akai MPC500 with various programs (drums, stabs, acapella chops, etc.), a Korg Kaoss Pad 3 with an Shure SM58 mike and a Korg microKorg, all MIDI clock-ed together, and all mixed into a Yamaha MG12/4 with a Boss SE-70 reverb send. There were also a 49-keys Casio keyboard and a Yamaha SHS10 mini handheld keyboard, both used as MIDI controllers to drive an EMU Turbo Phatt. Various circuit-bent toys were also pre-mixed and then fed into the Kaoss Pad as well, to get the best out of them.

Every machine has its own appeal: the Kaoss Pad 3 is the most appealing at first, but then it gets more difficult to master. The microKorg, thanks to its sync-ed arpeggiator and its modulation wheel is also rewarding very quickly. The MPC is somehow harder since you must be rather accurate when playing for the rhythm to sound good. The EMU Phatt is very easily rewarding, especially when using the Beats programs or other programs made of several sounds laid over the keyboard.

Fun or accurate: this is the question

One note about loops, either on the Kaoss Pad or in the MPC: if they help to improve the accuracy of the music (repeats perfectly each time), they also kill a lot of fun out of it since you only have to play once, record, and then you are done! On the other end, playing repeatedly the same thing (or at least trying to) helps to get warmer and warmer!

Thanks all for joining us for this party, and see you for next time!

Thanks Lai for the beautiful b&w picture!

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My First Circuit Bending

Last week-end I have bought five noise-making plastic toys at a yard sale in Paris; I then ordered knobs and switches from ebay and from a local electronic store. What for? For the purpose of circuit bending of course!

Noisy toys found in a yard sale
Noisy toys found in a yard sale

First failure

Out of the four toys, one was already non working when trying with new batteries. Once opened, there was nothing visibly wrong, every wire connected. Whatever what we do with it, only noise comes out from the two speakers.

The mini keyboard, already broken before any circuit bending
The mini keyboard, already broken before any circuit bending

Second failure

I searched how to start the art of circuit bending (I have been taught electronics in the academic fashion in engineering school, but I suspected circuit bending was somewhat different: usually in a lab, you do your best to avoid short circuits, at all costs!

The toy I killed by mistake
The toy I killed by mistake

I therefore read (but too quickly) the introduction by Reed Ghazala before opening the second toy. Then I started to short circuit each pin to each other while triggering the noises. After a few minutes, I believed I had found an interesting connection (as the sound was getting slightly strange) but immediately after, no more noise. I killed the toy.

Now I understand that having the sound slightly strange is precisely what we need to avoid. It was written in the guide…

Third try

Looking further I discovered additional advices (use only the body resistance to start connecting pins together, use a voltmeter to mark every high tension on the circuit to avoid them later).

The little music box, before anything happened
The little music box, before anything happened

Then it was quick since the circuit is so simple. I added a mini Jack output and checked it with headphones. I also added a switch on the output in order to interrupt the sound, and another (UPDATE) on the batteries wires to be able to shut down very quickly, just in case…

The inside with additional switches and Jack output
The inside with additional switches and Jack output

With only 4 resistors on the circuit it was easy to bypass them with my body resistance, and R2 is obviously controlling the pitch. So happy, this is really that simple. R2 is 100K?, so now I must test bypassing it with a potentiometer to find out the right value range to use. As it is all SMC (surface mount component) there will be some sport.

UPDATE I removed the 100K? SMC resistor that controls the pitch and replaced it with a 470K? potentiometer plus a serial 10k? resistor plus a serial switch to pause the playback (playback goes on where it was when switching back on, since the pause switch actually stops the clock to the chip).

The most difficult part was actually to put everything into the small box, without breaking anything.

It is a very simple circuit bending since only the pitch is controlled here.

Here is a demo video on Vimeo:

Scratching with a circuit bent jukebox toy from cyrille martraire on Vimeo.

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Geometric Rhythm Machine

In the post Playing with laser beams to create very simple rhythms” I explained a theoretical approach that I want to materialize into an instrument. The idea is to create complex rhythms by combining several times the same rhythmic patterns, but each time with some variation compared to the original pattern.

Several possible variations (or transforms, since a variation is generated by applying a transform to the original pattern) were proposed, starting from an hypothetical rhythmic pattern “x.x.xx..”. Three linear transforms: Reverse (”..xx.x.x”), Roll (”x.x.xx..”) and Scale 2:1 (”x…x…x.x…..”) or 1:2 (”xxx.”), and some non-linear transforms: Truncate (”xx..”) etc.

Geometry + Light = Tangible transforms

The very idea behind the various experiments made using laser light beams and LDR sensors is to build an instrument that proposes all the previous transforms in a tangible fashion: when you move physical object, you also change the rhythm accordingly.

Let’s consider a very narrow light beam turning just like the hands of a clock. Let’s suppose that our clock has no number written around, but we can position marks (mirrors) wherever on the clock surface. Still in the context of creating rhythms, now assume that every time a hand crosses a mark (mirror) we trigger a sound. So far we have a rhythmic clock, which is a funny instrument already. But we can do better…

Going back to our rhythmic pattern “x.x.xx..”, we can represent it with 4 mirrors that we position on a same circle. On the illustration below this original pattern is displayed in orange, each mirror shown by an X letter.. If we now link these 4 mirrors together with some adhesive tape, we have built a physical object that represents a rhythmic pattern. The rotating red line represents the laser beam turning like the clock hands.

Illustration of how the geometry of the rhythmic clock physically represents the transforms
Illustration of how the geometry of the rhythmic clock physically represents the transforms

Now we have a physical pattern (the original one), we can of course create copies of it (need more mirrors and more adhesive tape). We can then position the copies elsewhere on the clock. The point is that where you put a copy defines the transform that applies to it compared with the original pattern:

  • If we just shift a pattern left or right while remaining on the same circle, then we are actually doing the Roll transform (change the phase of the pattern) (example in blue on the picture)
  • If we reverse the adhesive tape with its mirrors glued on, then of course we also apply the Reverse transform to the pattern (example in grey on the picture)
  • If we move the pattern to another (concentric) circle, then we are actually applying the Scale transform, where the scaling coefficient is the fraction of the radius of the circle over the radius of the circle of the original pattern (example in green on the picture)

Therefore, simple polar geometry is enough to provide a complete set of physical operations that fully mimic the desired operations on rhythmic pattern. And since this geometry is in deep relationship with how the rhythm is being made, the musician can understand what’s happening and how to place the mirrors to get any the desired result. The system is controllable.

To apply the Truncate transform (that is not a linear transform) we can just stick a piece of black paper to hide the mirror(s) we want to mute.

If we layer the clock we just described, with one layer for each timbre to play, then again changing the timbre (yet another non-linear transform) can then be done by physically moving the pattern (mirrors on adhesive tape) across the layers.

From theory to practice

Second prototype, with big accuracy issues
Second prototype, with big accuracy issues

Though appealing in principle, this geometric approach is hard to implement into a physical installation, mostly because accuracy issues:

  1. The rotating mirror must rotate perfectly, with no axis deviation; any angular deviation is multiplied by two and then leads to important position deviation in the light spot in the distance: delta = distance . tan(2 deviation angle)
  2. Each laser module is already not very accurate: the light beam is not always perfectly aligned with the body. To fix that would require careful tilt and pan adjustment on the laser module support
  3. Positioning the retroreflectors in a way that is accurate and easy to add, move or remove at the same time is not that easy; furthermore, even if in theory the retroreflectors reflect all the incoming light back to where it comes from, in practice maximum reflectance happens when the light hits the reflector orthogonally, which is useful to prevent missed hits

Don’t hesitate to check these pages for progress, and any feedback much appreciated.

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Rhythmic clock machine

The rotating mirror and the 4 laser beams
The rotating mirror and the 4 laser beams

I finally received ten retroreflectors, the experiments started in Playing with laser beams to create very simple rhythms”, we can now move on.

Once again, the rotating mirror is reflecting the four parallel laser beams so that they sweep a 180 degrees area, where some retroreflectors are positioned to hit the beams trajectories.

Every time a beam hits a reflector then it should trigger a sound on a MIDI synth (here it is my little microkorg playing the sounds).

Generative music (a.k.a mangled rhythm)

However in the first try I forgot to set a short loop perid (the period was set to 100ms). Given the velocity of the laser beam when it hits the reflectors there is very little time to catch the signal on the sensors, and with a measure every 100ms the Arduino is missing most hits.

This means we got a simple and regular theoretical rhythm that is mangled by the input sampling process, and this fuzzyness actually creates “interesting” generative music, as in the video:

Generative music installation with laser beams and low-frequency sensors sampling from cyrille martraire on Vimeo.

Note that it is not totally random… (actually it is not random at all, just the result of different frequencies that sometime are in sync and most times are not).

Laser beams on the wall
Laser beams on the wall

Regular rhythm at last

With a shorter Arduino loop period (10ms) it becomes reliable: every (almost) hit triggers a note, as illustrated in the next video where we can hear a steady rhythmic pattern.

The Arduino code is quite simple: for each of the 4 sensors, read analog value, compare to threshold, debounce (not to send multiple notes for the actual same hit), then send MIDI note.

Arduino code for the rhythmic clock project

Laser beams generate regular rhythm at least from cyrille martraire on Vimeo.

Any feedback welcome…

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Playing with laser beams to create very simple rhythms

Just like many arts, music arousal is considered to follow the well-known Wundt curve that defines the balance between attractiveness and boredom. Too much repetition is boring, not enough repetition is confusing and considered just noise.

What for?

Let us assert that idea to music, to generate rhythms. A very simple application of the Wundt curve principle is to consider one given rhythmic pattern (e-g. , “x.x.xx..”) then to build up a more elaborate polyrhythm by combining various repetitions of it, although each copy must be distorted a bit to make the combination more complex hence more attractive. In other word, given a rhythmic seed, make it grow a rhythmic tree.

The transforms to apply to the rhythmic patterns can be linear:

  • Reverse (“..xx.x.x”)
  • Roll (“x.x.xx..”)
  • Scale 2:1 (“x…x…x.x…..”) or 1:2 (“xxx.”)

or non-linear:

  • Truncate (“xx..”)
  • Switch timbre (not really a transform, just to put somewhere)

In practice

To put that into practice I have been trying simple Java programs long ago, but it was too slow a process, and since I did not build a genetic algorithm around it was driven at random.

To make it more fun to investigate, we have started a small project of building an instrument to program rhythms on using laser beams and small reflectors. Each reflector triggers a sound (on a MIDI controlled MPC500) when hit by a laser beam (you need the sound on to listen to the Clap sound being triggered):

Playing with the beams to create very simple rythms from cyrille martraire on Vimeo.

The Arduino board
The Arduino board

Then by having several reflectors linked to each other to make patterns, we expect to be able to program rhythms by moving reflectors sets in the playground, using its geometry to derive the transformations to apply to the patterns.

EDIT: here is another video after some progress:

Playing with dual beams for kick and clap beat from cyrille martraire on Vimeo.

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