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Synthesis Tutorials

Faking Fake Chords on the ARP Odyssey: The ChipB4Chips Patch by Amplitude Problem

Video version in case you don't feel like reading

In the past, I made a tutorial for playing chords and melodies simultaneously on the Moog Sub 37 using 8-bit home computer techniques. It's no secret that I love the distinctive sound of an ultra-fast chip arpeggio, which is what the technique relies on to give the illusion of a chord. So, when I recently received Korg's amazing ARP Odyssey re-issue, which is paraphonic like the Sub 37, I had to give it a shot on that synth as well. It turned out to be more challenging, but completely possible, to achieve a very close sound.

Hardware constraints in the form of limited voices were the reason the chiptune chord technique was invented in the first place, and while the Odyssey is a fantastic analog synth, it has very limited polyphony. More limited, in fact, than early computer sound chips such as the POKEY and SID. Further complicating matters is the fact that, unlike the Sub 37, it has no built-in arpeggiator. Now, I could cheat and use an external MIDI sequencer to very easily arpeggiate chords on the new Odyssey, but the original 1972 model came out a decade before MIDI was introduced, so I'm going to stick to what can be achieved by playing live using only the Odyssey.

The idea that this iconic sound could have been approximated on an analog synth in the early 70s sort of blows my mind, and I'm left wondering whether anyone put a similar technique to use back then for the purpose of playing chords. I've certainly never heard any recordings of it from that time period; please let me know if you have.

By the way, there is a way to make the filter self-oscillate and then tune its frequency, in effect creating a third oscillator. This technique can also be used to play chords but the resulting sound is very different from what we're going for here.

So, because it has no arpeggiator, we can't fake chords on the Odyssey using ancient home computer techniques, but we can fake those techniques, in effect faking fake chords!

We're going to put both oscillators to use. Since both of them will be playing parts of the same chord, we want them to have very closely matching timbres. So, in the Audio Mixer section, set both VCO-1 and VCO-2 to the square wave position (down). Make sure both oscillator levels are high enough that you can hear them and then adjust their frequencies to identical tunings in their respective Frequency sections.

Now, also in the Audio Mixer section, let's turn the volume of Oscillator 2 all the way down to zero, leaving us only with the sound of Oscillator 1, which should be turned all the way up to 4. We're going to create a fake two-step arpeggiator for Oscillator 1 by setting its LFO selector to square wave (down). This will cause it to alternate between two values. We want the first value to be the tonic of the chord and the second value to be a perfect 5th up from that. If your LFO Frequency is set too high at this point, it can be difficult to make out the pitch interval, so you can always turn it down to a low value in the Low Frequency Oscillator section while tuning your chord. Use Oscillator 1's FM LFO slider to achieve the right pitch for our 5th. That's about 2.65 on my slider but use your ears. Once you can hear the Odyssey toggle between the tonic and 5th, you can turn up the LFO Frequency pretty high until the two notes form more of a continuous sound than separate ones. I like mine between 3 and 3.3.

Why are we telling Oscillator 1 to play the 5th instead of a 3rd? The reason is simple: if we tune to a 3rd, we're locked into either major or minor and will be very limited in terms of what chords we can ultimately play. But the tonic and 5th exist in all basic triads so we're safe locking them in. Taking advantage of the Odyssey's paraphonic nature, we're going to get our 3rd using Oscillator 2 so that we can switch between major, minor, suspended, etc. at will using the keyboard.

Let's turn the volume of Oscillator 2 back up in the Audio Mixer section. Since Oscillator 2's LFO selector doesn't have a square wave option, we can't alternate between pitches like we do with Oscillator 1. The result is a constant pitch which will sound louder than what's coming out of Oscillator 1. Therefore, I find that Oscillator 2's volume needs to be a bit lower than Oscillator 1's, about 3.5.

The last thing we're going to do is destabilize Oscillator 2 a bit. The reason for this is that its constant pitch doesn't blend with Oscillator 1's alternating frequencies very well, breaking the illusion to an extent. To make this job easier, mute Oscillator 1 by turning its volume all the way down. Set Oscillator 2's LFO selector to sine wave (up) and turn its FM LFO slider up to about 1.3. This will cause a vibrato effect at the same rate Oscillator 1 is alternating tones at, which I find blends the whole thing together much better. Finally, turn Oscillator 1's volume all the way back up.

Now, the way to make use of all this work is by playing the 1st and 3rd of your chords on the keyboard. You'll hear a good approximation of a high-tempo arpeggiator faking a chord.

You can even play a melody on top of your chord since Oscillator 2 will simply grab the highest note played, which is the melody, while Oscillator 1 keeps alternating between the 1st and 5th of your chord. So you're temporarily swapping out the 3rd for a melody note while you're sustaining it, and then when you release, Oscillator 2 will return to filling out the triad with the 3rd.

The keen observer will already have figured out that you can substitute the 3rd for any chord note instead of a melody note. Suspended chord notes and extensions work great. Whatever else you layer on top, the tonic and 5th will remain constant. If you manually alternate between the 3rd and 7th, for instance, you can achieve some pretty colorful, jazzy results. You can even add a 9th by stabbing quickly with the 5th at the bottom, filling it out with the 7th on top.

As for filter and envelope settings, you can play around and see what you like. I keep my settings very basic for this patch because it suits the sound. So, I'm not cutting any frequencies and I keep the ADSR envelope with only the Sustain turned up, although some Release can sound very good when moving through a chord progression. Please check the photo to see all of my settings if something doesn't sound right.

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Making the Moog Sub 37 Scream Like an Electric Guitar: The EGuitar Patch by Amplitude Problem

Video version in case you don't feel like reading

In my last Sub 37 tutorial, I explained how to take advantage of the Sub's unique Duo Mode combined with the arpeggiator to emulate playing both chords and melodies at the same time. It got me thinking about what other dark arts Duo Mode could be useful for.

The Sub 37 can be a rather gritty-sounding synth. Running different frequencies on the two oscillators, especially with their mixer levels way up, can definitely increase the grunginess. So, grunge plus the ability to play two notes simultaneously equals electric guitar power chords! Or at least some sort of approximation. Let's also see how close we can get to an electric guitar sound when playing this patch as a lead as opposed to power chords. We'll do all of this without using any external effects or it wouldn't be any fun.

First, select an available, newly initialized patch that we can work on, and where you can save the EGuitar patch when done.

Let's go from left to right. The Arpeggiator isn't important in this case, so you can set it however you like later on. For now, let's turn it off. Do the same with Glide. I found a Time value of 2 with Type set to LCT sounding fine, but again, let's turn it off for now. I find that this patch sounds best in the default Keyboard Octave and also one octave above that.

For Modulator 1, set the LFO Rate to 12 and the Source to Triangle. The Pitch Amount should be just above 0 and this should affect both oscillators. Set the Filter Amount and Modulator Amount to 0. We'll tie this modulator to aftertouch so we can get a little vibrato without reaching over to the mod wheel. Press the Modulator 1 Controllers button and use the digital Programming menu to achieve this.

Modulator 2 should look identical to Modulator 1 but you can increase the Pitch Amount just a hair. We'll bind this modulator to the mod wheel so you can call upon just a bit more vibrato when required. Press the Modulator 2 Controllers button and again use the digital Programming menu to make this setting.

Moving on to the oscillators, we're somewhat ironically going for tame waveforms, setting both of them to 8 feet and Triangle. For Modulator 2, let's set Keyboard Control to High and of course turn Duo Mode on. Finally, the value for both Frequency and Beat Frequency should be 0.5. This slight frequency variance will cause an interesting de-tuning and phasing effect, which you can alter by trying different values for Beat Frequency.

In the Mixer section, we're going to turn both Oscillator 1 and Oscillator 2 all the way up to 10. We're not going for careful gain-staging here. However, I don't like a lot of Sub for this patch, so let's only turn it up to 1.2. We'll add a tiny bit of Noise for good measure, setting it to 1.1. Feedback gets turned all the way up; this is at the very core of this patch as it creates massive amounts of distortion when feeding the mixer output right back into the mixer. You can truly start hearing the clean and mellow flute-like sound of the triangle waves radically change once you approach and pass 7 on the Feedback knob. Please watch your output level when turning up Feedback. Finally, make sure that everything in the Mixer section is turned on.

Let's leave the Filter at 20KHz so we can hear all the upper-end screaming of this patch. Resonance should be at 0 and Multidrive at 4.2, which will beef the whole thing up even further. Again, please watch your output level. You might be tempted to crank up the Multidrive distortion all the way, and please feel free to do so. However, I found 4.2 to be a nice-sounding spot. We're going to turn both Envelope Generator Amount and Keyboard Track to 0.

The last section is the Amplitude Generator where we set the ADSR. I like a very short Attack for this patch; let's set it about one mark below 10. Decay can be turned all the way up to 10 Seconds. Let's dial in a Sustain of 1.5 and a Release two marks below 1. This will give us a nice, relatively slow fadeout when holding notes. Finally, let's turn on Multiple Triggering to ensure the envelope is re-triggered with each key press.

You're now ready not to pretend you're a guitar player, but to show the world that the analog Moog Sub 37 can wail with the best of them without running it through a guitar amp or other silly things. Adding an external delay to the EGuitar patch makes it even more fun to play! Try out some power chords and play a melody, occasionally adding that second note and pitch bending the whole mess. Turn on a drum machine and you might sit there jamming for a while.


Playing Moog Sub 37 Chords and Melodies Simultaneously Using 8-Bit Home Computer Techniques: The SIDlive Patch by Amplitude Problem

Video version in case you don't feel like reading

Back in the 8- and 16-bit eras when we made music on limited — but awesome sounding — three-channel hardware like the SID 6581 in the Commodore 64 and the YM2149 in the Atari ST, we used a certain trick to play chords using just a single channel. This way, the remaining two channels could still be used for melodies, bass lines and drums. The trick was simply to loop an extremely fast, usually three-note, arpeggio on a single channel. When looped fast enough — much faster than a human can do manually — our ears will pick this up as something chord-sounding and not quite as individual notes anymore. Think of it as audible, time-sliced multitasking. It got crazier than that, with different instruments using time slices on the same channel, which in fast-tempo songs created the illusion of more than three channels, but that's something for another day.

Many users of monophonic synthesizers are probably familiar with this technique as well. You can use an arpeggiator, if available, at a very high speed and then hold down the keys constituting a chord, and you'll hear a very similar effect to the one described above. For chord notes, this technique is sufficient — even cool sounding — but a problem arises when you want to play a melody over the chords, say, in a live setting. Since you only have one voice, the melody note has to wait for the arpeggiator to play through the rest of sequence before it reaches it. Only then will it be heard, and only for a brief time. It kind of works with slow melodies but it's far from optimal.

A related technique, if an arpeggiator isn't available, is to set a modulator to square wave mode with its LFO set at a high rate, and route it to the oscillator's pitch. The modulation pitch amount is then set to a minor or major third, a perfect fifth or perhaps an octave. This will give a similar illusion of a chord being played, albeit just a two-note one, which makes extended chords especially impractical. Another problem with this method is that if you wish to use thirds, you lock yourself into either a minor or major chord, making the sound much less flexible than when playing broken chords in real-time using an arpeggiator. A way around this limitation is to use two or more patches with different values for the pitch amount. By switching between patches, you can awkwardly play chord progressions using the modulation method, but not even a trace of a melody.

As the name implies, the Moog Sub 37 has a 37-note keyboard, which makes you want to play chords and a melody at the same time. It also has something rather unique among analog synthesizers called Duo Mode, which allows the synthesizer to play its two oscillators at different pitches, controlled by two keys on the keyboard. It seemed like this mode could be combined with the arpeggiator to facilitate simultaneous comp plus melody if I employed some ancient techniques from the home computer era.

Let's make a bleepy, bloopy and crunchy approximation of a SID-style instrument with some cool capabilities!

For Oscillator 1, I'm going with a straight up square wave and an Octave setting of 4 feet.

I'm interested in achieving that broken chord chip sound from the voices themselves, before we even bring the arpeggiator into the picture. So, I'm setting Modulator 1 to use a square wave with the LFO set at a relatively high rate, just below the 25 mark, and the Pitch Amount to one octave, which is roughly one-third past the second mark, affecting only Oscillator 1's waveform.

(To get the Pitch Amount right, it can be helpful to temporarily slow down the LFO so you can clearly hear alternating octaves, and then turn the LFO back up again.)

For a nice, full sound, I'm using a sawtooth wave for Oscillator 2, also with an Octave setting of 4 feet. If you really want to span a lot of frequencies, try bumping this up to 2 feet. For me, the result of that is a bit too bright.

In order to facilitate our ultimate goal of playing both looping broken chords and a melody at the same time, I'm selecting Duo Mode and setting Keyboard Control to High. This way, Oscillator 2 will be in charge of the melody that we'll play highest up on the keyboard.

The settings for Modulator 2 are almost the same as for Modulator 1, the major differences being a slower LFO rate, just above the 12 mark, and targeting Oscillator 2 rather than Oscillator 1. You can play around with the LFO rates and see what you like.

In the Mixer section, I'm cranking up both oscillators to 11 but leaving the Sub Oscillator's level down a little, around 7, as I find it overbearing when maxed out for the particular sound we're creating. I'm dialing in a barely noticeable amount of noise for some added crunchiness found in many SID and POKEY sounds. If you favor a cleaner sound, just turn Noise off.

A high Rate on the Arpeggiator is critical to being able to play looping broken chords, so I'm setting it to 220 BPM, which is very fast but just slightly more relaxed than maxing it out. I'm avoiding Back / Forth because I want every note in the arpeggio to play as frequently as possible as this is critical for tricking the ear. You can set Pattern to either Up or Down based on personal preference. And of course, make sure the arpeggiator is turned on.

Use whatever Filter setting you desire. I set the Filter Multidrive to about 3. You can play around with the Amplitude Envelope to see what you like. The Attack has to be very short, however, so that each note has time to play at a good level before the arpeggiator triggers the next one. I like just a slight Release on my chip sound to give it a nice fade-out and I also turn on Multiple Triggering.

If you just want to play a bass line plus a melody, simply turn the arpeggiator off for added response to your bass notes. In this mode, you can also play two-note chords, for example the 1 plus either a minor or major third. This will sound very 8-bit as well. For even more color and authenticity, you can make one LFO alternate between the 1 and the 3 and the second LFO alternate between the 5 and the 8. This will sound beautiful but of course you're then locked into either minor or major chords since the 3 is hard-coded into the LFO. For quick and accurate chord changes, it's best to stick with the arpeggiator method.

Finally, you can set the Pitch Amount on both LFOs to zero, which will remove the alternating-octaves effect and create a less 8-bit sound, but the world needs more chip, not less, so why would you?
