The BeatBearing Tangible Rhythm Sequencer

By Peter Bennett
Category: Music
Difficulty: Moderate

The BeatBearing is an exciting and intuitive way to make music. Move the balls on a grid, and you change the beat. Music sequencing couldn’t be simpler.

Like countless other musicians, I use a computer to create beats and sequence them into mixes. Pointing and clicking with a mouse is fine for a studio, but what about when you want to sequence rhythms in live performance? Or collaborate with others on a shared rhythm? These questions led me to develop the BeatBearing sequencer.

So what is the BeatBearing? Simply put, it’s a computer interface that takes the pattern of ball bearings placed on a grid and translates it into a rhythm. The fun part is that the whole interface is transparent and sits on top of a computer screen, allowing graphics to be shown from directly underneath. The screen highlights which beats are switched on, and what sounds they’re playing, as a red line sweeps across the screen to show the current time position. The system is controlled by an Arduino microcontroller, and the screen is an old computer monitor cradled in a milk crate.

Steps

Step #1: Split the washers.

I had these washers split and drilled by a milling machine at Queens University Belfast’s friendly engineering department, but you can achieve similar results using a band saw and a drill press as follows. Alternatively, you can bypass the washers altogether and make ball-bearing contact switches more easily out of bent wire, or with screws or metal pins arranged in a triangle or square. See the files section for sketches.
Clamp and drill the washers in a drill press, centering the 2 small holes on opposite sides of each.
Use a band saw to cut each washer in half, perpendicular to the axis formed by the 2 holes. It’s easier if you clamp or screw the washer to a jig of scrap metal or wood.
File off any sharp edges. The washers will be exposed to fingers when installed on the instrument.

Conclusion

Tangible User Interfaces

I first encountered tangible user interfaces (TUIs) at the Ars Electronica exhibition in 2003, where I saw James Patten’s Audiopad project and Sony CSL’s Block Jam. These TUIs, along with others I have since found, inspired me to pursue a Ph.D. to study and develop new musical instruments, and influenced my design for the BeatBearing.

The main idea behind TUI design is that the user should be given a physical handle on the digital data. Importantly, this handle should allow the user not only to feel and see the data, but also to grasp and manipulate it. In the case of the BeatBearing, you “read” and manipulate the sequencer through the arrangement of the balls.

One design challenge I’ve found with TUIs is how to include a visual display. Typical computer game interfaces (and others) have you look at the screen while manipulating a controller elsewhere. Many TUI researchers create more direct connections by projecting an image onto a control surface from above or below. I’ve tried top-projection with instruments I’ve designed, but found it cumbersome, especially if you want a portable instrument for playing live. My solution for the BeatBearing was to ditch the expensive digital projector and show the visuals from below using a cheaper CRT.

I deliberately designed this project to be a base upon which further tangible interfaces could be developed. I believe it has the potential to do much more than this original version.

Modifications

Each part of the BeatBearing is simple enough to allow for easy modification. Here are some ideas:

Tweak the Processing code to change the graphics. How about showing the name of each sample?
Add a tempo control in the software, or add a dedicated potentiometer to the hardware.
Build the BeatBearing into a coffee table, wooden cabinet, or my favorite, an old leather briefcase.
Add extra “sample select” holes to one side of the grid, allowing you to switch between sample banks directly from the board.
Expand the grid. A 16×4 grid would be large enough to create more serious rhythms.
Use a flat LCD monitor instead of the bulky CRT — a bit more expensive, but much more portable.
Write new software. You can use the program provided, but if you want to develop your own firmware, the pseudo-code is:
1. Set address lines on the multiplexers.
2. Read analog pins.
3. Repeat Steps a and b to read all the positions on the grid (cycling from 0000 to 1111).
4. Send out the values of all grid positions over serial.

Different software applications are possible; for example, rather than a sequencer, how about a real-time performance instrument?