A-01 CONTROLLER + GENERATORThe Story Behind the Development of the 8-Bit CPU Synth

The Story Behind the Development of the 8-Bit CPU Synth

One prominent feature of the Roland A-01 is that it's equipped with the "8-Bit CPU Synth," a unique sound-engine circuit like no other. Just as its name suggests, the 8-Bit CPU Synth is a "virtual analog" digital sound engine that reproduces a subtractive synthesizer with an 8-bit CPU. While there are many products that advertise to be virtual analog, this synth―with the limited computing resources of its 8-bit CPU combined with a lo-fi 10-bit DA converter―is truly capable of producing tones with unique analog textures. Its sound, which is perhaps rightfully described as "vintage digital," is sure to entice synth enthusiasts around the world.

It was Akira Matsui, a former Roland engineer, who came up with the basic design of the 8-Bit CPU Synth. After joining Roland in 1977, Matsui had been involved in the development of a variety of products, including company classics such as the SYSTEM-700 and SYSTEM-100, as well as the early GR-series guitar synths. Of the many products that he was involved with, the most prominent was the JX-3P. Released in 1983, it's known as one of the first synthesizers to support MIDI, and has been highly praised for its colorful and expansive sounds. This synth was also the inspiration for the Roland Boutique Series JX-03, which was released in 2015.

After retiring from Roland in 2013, Matsui immersed himself in his hobby of making electronic devices in his home studio. This is where the 8-Bit CPU Synth was born, which is now featured in the A-01. A Roland staff member who happened to see the homemade synth was instantly intrigued and approached Matsui to learn more about it.

This is the story of how the 8-Bit CPU Synth―which Matsui made as a part of his hobby―ended up in the A-01, and how a renewed collaboration began between Roland and one of its legendary engineers.

Akira Matsui is a legendary Roland engineer who was involved in the development of many classic products, including the JX-3P synth.

You are known as the originator of one of Roland's classics, the JX-3P. Did you first join Roland because you wanted to make synthesizers?

Matsui:Yes. Synthesizers first came out when I was a student. They had a stylish aura and I was quite intrigued. So when articles began to appear in magazines on how to make synths, I would go through those and begin making my own. I soon realized that a synth wasn't quite a synth without a keyboard, so I remember cutting blocks of wood with a jigsaw to make the black and white keys, although I have to admit that I gave up about half way through an octave! [Laughs.] In any case, I just liked to tinker with things when I was a student, and I liked things that "made sounds," so that's why I applied at Roland.

I joined the company back in 1977, and I started off doing assembly and inspection work on the SYSTEM-700 and SYSTEM-100 at the Osaka factory. Soon after that, I was put in charge of circuit design. In those days, we didn't have the convenient tools that we have today, so we would take out a blank circuit board, draw circuits on them with permanent ink pen, and etch them with ferric chloride to make patterns. [Laughs.] After three years in Osaka, I was transferred to Matsumoto, and once there, I was involved in the development of the guitar synth. In the development of the GR-700, I was involved from the basic research stage.

What are some of the products that you have the most memories about when you were working at Roland?

Matsui:That would have to be the JX-3P. First off, it was the first synth that came with MIDI support, but another memorable thing for me was that it was the first synth that I programmed the microprocessor for. Up until then, I had been working almost exclusively on analog circuitry design, so I remember having a tough time programming the microprocessor. But since development processes are essentially a challenge into new territory, it was a lot of fun. It was quite difficult in terms of sales back in those days, but the JX-3P managed to make a positive contribution to sales for the Matsumoto factory.

The next product that I remember the most would have to be the VS series. The series' concept was to have a single unit that could transform any room into a studio, so they came integrated not only with a recorder, but also a mixer and effects. This was a perfect match for the needs of that era and the series became a huge hit. The VS series employed a compression scheme called "R-DAC" that enabled users to make longer recordings on limited hard disk space, and I believe R-DAC's natural sound was a major contribution to the series' popularity. MP3 had just started to come out, and while MP3 would trim off quite a bit of audio information, R-DAC would generally leave the audio information intact, so it would retain the nuances of the original sound.

Since you retired from Roland in 2013, you have immersed yourself in your hobby of making electronic devices.

Matsui:For many years since I joined Roland, the company has given me the freedom to develop products the way I wanted to as an engineer, so I am very grateful for that. But towards the end of my career, I was in a management role, so there was this constant hunger for "making things with my own hands." So after retirement, this urge exploded all at once, and I've been tinkering with solder gun in hand ever since. [Laughs.] I've even purchased a laser cutter and 3D printer, so now I have a setup where I can make whatever I want the moment I have an idea.

I've made a lot of things in the two years after retirement. I made a helicopter for aerial photography, something like the drones that have become popular in recent years, and a table clock based on a VU meter. I also had this unstoppable urge to solder things, so I went to a home hardware store, bought huge amounts of brass nails, and soldered them all together into a remote-controlled model car. When I look back, I may have just wanted to sniff the smell of soldering paste. [Laughs.] I also do woodworking and welding.

The 8-Bit CPU Synth is a sound engine that was born as a result of challenging the limits of running on an 8-bit CPU and 8 KB of memory.

So you've been enjoying making things at home to your heart's content. What made you think of developing a synthesizer again?

Matsui:All the while that I was making these things, I was still interested in sound. So I had this vague desire to eventually make a synth. Nowadays, we've got cheap ARMs and CPUs so anyone can go out and make a decent digital synth if they wanted to. And I'd made plenty of analog synths on my own when I first joined Roland, so I didn't feel any excitement there either. And then one day I wondered what it would be like to make a synth with an 8-bit CPU. The idea was to see how far I could go with the limited resources of an 8-bit CPU and 8 KB of memory. I think this was in early 2014. The first thing I programmed was the oscillator, and somewhat surprisingly, it ended up being something that you could play decent scales on without using a lot of resources. I then programmed all of the analog synth elements―the filter, followed by amp, and then LFO―and I was able to pack all of them in quite nicely. In the remaining space, I programmed a step sequencer, and the finished result was the 8-Bit CPU Synth.

So you deliberately applied a set of obstacles―in this case an 8-bit CPU and 8 KB of memory―because anyone could easily make an ordinary synth?

Matsui:Something like that. You could say that I wanted to see how far I could go with an 8-bit CPU and 8 KB of memory. [Laughs.] If you're into making things, it's often a lot more fun when you have these kinds of obstacles.

When you hear "8-bit," what comes to mind is the chiptune sound engines used in game consoles. But the 8-Bit CPU Synth is a virtual analog digital sound engine that uses an 8-bit CPU to reproduce subtractive synthesizer circuitry. Is this correct?

Matsui:Yes, that's correct. It has one oscillator, filter, envelope generator, amp, and LFO. It has four oscillator waveforms (sawtooth, square, pulse, and noise) and four LFO waveforms (sine, triangular, sawtooth, and random). On the filter, I reproduced the effects of state-variable type filters.

Did you think of adding unusual waveforms or features that you could get only on digital sound engines?

Matsui:The concept for the 8-Bit CPU Synth was to make, on an 8-bit CPU, a straightforward reproduction of the algorithms used in the good old days of analog synths, so including unusual functions was never on my mind. Even when you say "sawtooth wave," I personally have my own idea of the "ideal sawtooth wave," so I wanted to reproduce that on an 8-bit CPU. Same thing with the envelope generator—I wanted to make a straightforward reproduction of an analog synth envelope that is generated with resistors and capacitors. That said, there are areas where I've kept the advantages of digital. For example, you can set the LFO's frequency quite high, so when you modulate the oscillator in that state, you get a kind of FM-ish or digital synth-ish sound.

I was impressed with the unique presence of the sound, which is distinct from either digital or analog synthesizers.

Matsui:Some of the virtual analog synths output their oscillator waveforms as samples, but the oscillator on the 8-Bit CPU Synth actually oscillates. The noise is made from oscillations too.

I wanted to see what I could do within the limited resources of the 8-bit CPU and 8 KB of memory, but it wasn't actually that difficult to reproduce the functions of an analog synth. Had I left it at that, however, the sound would have been quite feeble, so I spent a lot of time tuning the program. There's no point in having a synth with lousy sound. But if you begin making elaborate tunings in your effort to improve the sound, you will quickly run out of your 8 KB resource limit. So you do your tuning, but also make sure that the program fits into 8 KB. I think this is what makes the 8-Bit CPU Synth's sound so unique and distinct from modern synthesizers or software sound engines.

So in tuning your program, was it a process of listening to the sound and going through many trials and errors?

Matsui:Yes, that's right. Tuning synths ultimately comes down to trial and error, and theory kind of goes out the window. [Laughs.] This is also true for analog synths. You just start off playing its sound and you rely on your ears to tune it. So you do it with repeated trials and errors.

"I've obsessed with the sawtooth wave in developing this, so whatever else people do, I want them to listen to this sound."

What were some of the areas that you had a hard time with during development?

Matsui:The top on the list would be noise. The 8-Bit CPU Synth runs on a 48 kHz sampling rate, and does all of its computing within that frequency, and the noise is the biggest resource hog. Since I've been involved with analog synthesizers for so long, I can't settle for just some vanilla version noise. [Laughs.] I wanted a pleasant kind of noise that people could use in sound sculpting, so I spent a lot of time on that.

And so the 8-Bit CPU Synth that you've developed as part of your hobby will be integrated in Roland's new A-01 product. How did this collaboration come about?

Matsui:When I finished my first prototype of the 8-Bit CPU Synth, I exhibited it at the Maker Faire Tokyo 2014 (a fair for individuals and organizations engaged in "making things" [monozukuri]). A person from Roland saw it and liked it, and that's how it got to be included in the sound engine section of the A-01. As a result, the A-01 has become quite an interesting product. It would have been unique enough being a USB MIDI controller with Bluetooth MIDI and CV/Gate output, but it actually also comes with a built-in 8-bit synth. [Laughs.]

As a former Roland engineer, what do you think of the A-01?

Matsui:I think it's a really interesting product. The sequencer I made for the 8-Bit CPU Synth is very simple, but the A-01's built-in sequencer can do shuffles among other things and is quite powerful. On top of that, the knobs are really great. These are volume knob-type encoders, and when you turn them they have that really pleasant clingy feel. Even from an engineer's perspective, you could see the obsessive attention that went into this product.

The 8-Bit CPU Synth gives users the ability to make a variety of sounds such as bass and lead, but are there any tones that you as the developer would recommend?

Matsui:Let's see…I've been a huge fan of sawtooth waves over the years, so I'd be happy if people listened to that, whatever else they do. I think it's got a great persistent tone where, if you are a fan of sawtooth waves, you might think to yourself, "This is all I need." [Laughs.] Incidentally, the A-01 will ship with 16 factory presets, so I'm looking forward to hearing what kinds of sounds the people at Roland come up with.