Sometimes, DIY music boxes reach moments of mad genius. To me, they’re almost a kind of compositional conceptual art, executed as a set of circuitry and disguised as a piece of music gear. They assemble in series a set of solutions to design problems, but result in something – through the combination of invention and throwback, simplicity and absurdity – insane and wonderful.

At least that’s how I feel when I look at the Drumssette, the latest invention from musical instrument engineer Mike Walters. It’s a combination of the innards of a Tascam four-track cassette recorder with a push-button, gated sequencer, making a tape-based drum machine. (It makes sense coming from Mike Walters, who in the past demonstrated a Mellotron made from Sony Walkmans. The Drumssette is the drum machine equivalent of the earlier Melloman.)

The Drumssette, by Mike Walters

The trick to making a cassette tape into a drum machine is twofold: loop the drum sounds onto the tape itself, then route that audio output as the clock signal that drives the sequencer. With that done, you only have to push the buttons to turn the sounds on and off on the beats you want. There’s a bonus, too: what Walters calls the “focus” knob controls a delay line, allowing you to shift the position of the played-back sound forward or backward to control the sound’s attack.

In a way, it’s a reinvention of what the Tascam tape deck was – or, to look at from the opposite angle, a re-imagining of drum machines in a world in which digital recording was never invented. Its bright color scheme and throwback light-and-knob design underline the alternative-universe vision.

Tricks are treats

It’s the details of the path to this design solution that are daftly elegant.

For instance, there’s the “focus” knob, and the idea of using the delay line to control attacks:

Since the trigger for the sequencer clock is audio used in parallel with the actual sounds of the instrument, the triggered audio from each track might lose a bit of its attack when it gets to the output, especially if the sound has a slower attack. To solve this, I built a delay stage before the parallel audio gets to the sequencer. This audio does not go to the output of the Drumssette. Using a PT2399 digital delay chip, the parallel audio signal is treated with a simple, adjustable delay, with no feedback (repeat stages) and a clean output. Delaying the audio signal before it becomes the clock signal allows the the operator to apply an adjustable delay parameter to the sequencer, which allows the gating to scoot over and focus on the next drum sound on the tape before the loss of attack. This happens because the audio on the cassette is time constant, and the delayed signal is variable. The momentary unmuting (gating) is dictated by the delay signal. You can also focus between sounds, to create double time beats.

The innards of the Drumssette, and its cassette tape soul. (And they say drum machines have no soul.)

Then there’s the efficient, unexpected use of optocouplers and light sensitivity to produce a time-synced echo:

The analog method is different. When this mode is selected, the audio from the tape is passed through a photo-resistive circuit using optocouplers. Optocouplers are little capsules with photoresistors and LEDs inside. Photoresitors become less resistive with more light, so when the LED is on, they suddenly drop to a few ohms. When the LED is off, they go back to a couple mega ohms. The photo resistive material, Cadmium Sulfide, retains some light energy between stages. So, as opposed to a switch, the optocoupler fades in and out the signal much slower. This gives the sounds a synchronized echo (you can hear the next four or so drum steps on the tape as it fades out). This mode actually uses two optocouplers, and an inverter. These are wired in parallel to pass the signal when triggered, and then ground the signal when the gate is low. When the gate is low, the inverter changes the logic, switching optocoupler LED 1 on. When the gate is high, LED 1 turns off, and optocoupler LED 2 turns on. So, the signal is always passed or grounded in this configuration. If the signal is not grounded, there will be a little bit of signal bleeding to the output.

In Action

These videos really demonstrate that, aside from being a crazy design, the Drumssette is eminently usable as an electronic instrument. (It isn’t hard to imagine switching this on for a dancefloor, even.)

First, a look at how you can gate an external source using the sequencer for rhythmic external textures, in place of the “installed” drum sounds:

In this demo, I bypassed tracks 1 and 2 of the cassette by plugging in external sources – a Yamaha CS01 synth, and a turntable. The bass and snare come from the cassette tape. The rhythmic keyboard phrasing is completely controlled by the Drumssette. I was just holding notes down on the keyboard, and the states of the switches turned on and off the audio as the sequencer clocked. Same thing with the record on the other track.

Here’s a similar example, this time using a lovely sound from the Polymoog:

In this demo, I bypassed track one and two of the cassette tape audio, and replaced track one with the output of my Polymoog 280A on Vox Humana. The bass drum and snare sounds are from the cassette tape, which is also clocking the sequencer (snare sound, track 4). I’m simply holding down chords on the Polymoog, and the Drumssette is chopping them up according to Track One’s switch mapping on the front panel.

More Mystery Circuits Creations

The Drumssette is the self-proclaimed sequel to the earlier Melloman, a series of Walkmans connected to a keyboard for Mellotron-style cassette tape sampling. It’s now a five-year-old project, but no less stunning today as a benchmark of bizarre, fantastic design. The wonderful Analog Suicide (Tara Busch) took a tour of the Mellotron in 2008:

And these are just two among many, many creations. The full list:
Mystery Circuits

Retro Thing: Mike Walters Does It Again: Yamaha Keyboard + Heathkit = Mike-O-Wave

GetLoFi: Mike Walters’ Blue Boing (for a more compact creation)