Korg Arp 2600 for Mac/PC – the Synth and Software Review

An accurate reimagining of the original with many bonus features

Several companies – notably Arturia, Cherry Audio, and WayOutWare – have released software emulations of the classic ARP 2600 synthesizer. Korg, the company that resurrected the real-life ARP 2600 (calling it the Korg ARP 2600 FS, for full-size) in 2020 and the Korg ARP 2600 M (which is about 40% smaller) in 2022, recently introduced its latest version as a stand-alone application and plug-in in AU, VST, and AAX formats. You can run the plug-in as either an instrument or an effects processor. 

Like the original, the software is called simply ARP 2600. It’s part of the Korg Collection, an outstanding ensemble of virtual instruments that emulate classic Korg synths and effects from the past, available separately or as a bundle.

The original 2600 was the more portable and affordable successor to ARP Instruments’ massive modular system, the 2500. Available from 1971 until ARP’s demise ten years later, the 2600 is a semi-modular instrument. Its internal patch connections are hardwired so you can dial up sounds quickly, but you can also reroute those connections using patch cords.

During its first decade, ARP sold the 2600 in nine editions that differed in their oscillator and filter designs, color scheme, enclosures, and keyboards.

A personal note: the ARP 2600 was the first synth I got my hands on in college 50 years ago. Its manual (now a free download from Korg and written by Jim Michmerhuizen, founder of the Boston School of Electronic Music) was where I began my education in synthesizing sounds. I wanted to write this review to compare and contrast the Korg ARP 2600 software with the Korg ARP 2600 M synthesizer that I bought last year. Most of this review will focus on the similarities and differences between them.

Software vs. hardware

Like the original, ARP 2600 has three voltage-controlled oscillators (VCOs), a ring modulator, variable noise, a mixer, a voltage-controlled filter/resonator (VCF), a VCA with two modulation inputs, and 2-stage and 4-stage envelope generators. Also like the original, it has a reverberator, four voltage processors, sample & hold, an envelope follower, and a preamp for processing external sounds and using them as modulation sources. Most of them look and work the same as on the hardware.

Unlike the original, it also has two auxiliary LFOs (one specifically for vibrato), an auxiliary 6-stage envelope that loops, oscillators that sync, highpass and bandpass filter modes, a separate state-variable filter, gate and trigger controls, an arpeggiator, a step sequencer, and four simultaneous effects. With enough computer horsepower, it’s also polyphonic up to 16 simultaneous notes.

ARP 2600 divides its GUI into tabs. The Main tab is the synthesizer’s front panel, where you’ll spend almost all your time. Access to detailed parameters for the Effects and Reverb is behind tabs for those processors, and the Librarian tab lets you view and edit various data types and export files.

The Mod Matrix tab provides dozens of rows for assigning control sources (such as the mod wheel, aftertouch, note numbers, and MIDI CCs) to most synth parameters. Similarly, for real-time, hands-on control of the software, the MIDI Map tab assigns physical controllers on your keyboard or control surface to various parameters.

Making connections

Connecting outputs and inputs works much like in other modular software synths; just click and drag from one jack to another, and a patch cable will appear. Whenever you make a connection or hover over either end of the cable, animation indicates the direction of signal flow. That’s especially helpful when you’re trying to grasp complex patches.

When you select a connected output jack, another jack appears, providing as many mults as you need for every output – an outstanding feature. Compare this with only three dedicated multiple jacks in total on Korg’s ARP 2600 M. This is useful if, say, you want to use the noise generator to modulate multiple parameters or you want to control both the VCF and VCA with the ADSR generator.

Modular in a box

Although all internal signals are digital and exist only in software, of course, Korg refers to control signals as control voltages (CVs), as they really are in hardware. On the 2600 M synthesizer’s lower left, an unlabeled section has two CV outputs for pitch and another for modulation (CC#1) derived from the MIDI input.

The software’s GUI has a corresponding section labeled Control, with outputs for keyboard CV, velocity, aftertouch, the mod wheel, pitch bend, and any two MIDI CCs you select in the Settings dialog box. It also has knobs to determine aftertouch vibrato depth and pitch-bend range.

Just as on the real 2600, each of the three VCOs is different from the others. Each VCO is also identical to its hardware counterpart, with one exception: VCO 2 and VCO 3 each have a Sync button, which resets them to VCO 1’s frequency. When synced, VCO3’s controls affect timbre rather than pitch.

VCO 1 generates only sawtooth and square waves, while VCO 2 generates sine, triangle, sawtooth, and variable-width pulse. VCO 3 offers a choice of sawtooth and variable-width pulse. For each of the three oscillators, you can disable keyboard control (to use one as an LFO if needed), and you get three additional modulation inputs.

You’ll find more differences from the hardware in the VCF section. Whereas Korg’s updated 2600 hardware has a switch to choose between two lowpass filter designs from before and after 1975, the software adds selections for bandpass and highpass responses. Controls for filter frequency and resonance are identical to the original’s, but an additional resonance input and depth knob mean you can control the amount of resonance dynamically with an envelope, an oscillator, or any other control source.

The 2600 M has no dedicated LFO, forcing you to use a VCO’s lower frequency range if you need one as a modulator. That makes the software’s Auxiliary LFO a welcome bonus, then, with a curve control for more logarithmic or exponential response.

A second LFO dedicated to vibrato emulates the LFO on the vintage 2600 keyboard unit and offers a delay function.

But wait, there’s more

In addition to the 4-pole VCF, the software has a separate Mode-Sweep filter. Obviously inspired by Oberheim’s SEM filter, this is a 2-pole design with continuously variable lowpass, highpass, and band-reject modes, as well as a knob and a control input (hardwired to the sequencer) to sweep between modes. The Mode-Sweep filter has voltage-controllable resonance (also hardwired to the sequencer), but like Oberheim’s SEM filter, it does not self-oscillate.

Additional synth functions that don’t appear in the hardware include the ADSR time switch, which lengthens all four envelope stages, and the AR time switch, which lengthens or shortens both stages. The VCA has a Drive section that imparts saturation and overdrive. Two signal multipliers serve as VCAs for scaling one signal with another, whether they’re CVs or audio signals. I was also happy to see dedicated portamento and an octave-transposition buttons, two things I wish my 2600 M had.

Another module is the Keyboard section, which lets you choose whether the keyboard plays monophonically, duophonically, or polyphonically, plus you can specify note priority and trigger mode. It can also enable two types of latching and control note repetition to simulate tremolo picking.

To the right of the original controls are four slots for additional effects. One slot is dedicated to four types of reverb, but you can freely assign the other three to a selection of processors such as delays, guitar amp simulations, compression, EQ, and modulation effects such as chorus, flanger, phaser, tremolo, and rotary speaker.

All effects exhibit the quality you’d expect from Korg, and all supply numerous user parameters and presets.

Motion sequencer

Although Korg calls it a Motion Sequencer, the sequencer does not record real-time parameter changes as Motion Sequencers do on some other Korg instruments. In fact, it doesn’t record anything in real time, but it can still control parameter changes.

You program two independent step sequences, called lanes, by adjusting the positions of two parallel rows of sliders. Each slider determines the value, or voltage, of each step. Enabling the Pitch Quantize button ensures that the voltages match precise pitches for sequencing notes. Steps can also recall voltages you can route to any CV input to automate parameter changes.

You specify a maximum of 16 steps in each lane, as well as the start and end steps, whether and how many times it repeats, and loop direction. The ability to program the number of repeats is a standout feature, as is the ability to play steps back in random order.

You can assign MIDI CCs to modulate the step values and loop points, but you can’t use MIDI to enter step values. Many factory patches use the sequencer to great effect by adding motion to sustained sounds.

How does it sound?

Judging sound quality, of course, is the most subjective part of any review. To my ears, Korg’s ARP 2600 software sounds more realistically analog than any other soft synth I can think of. It also sounds more like my Korg ARP 2600 M than even other hardware clones I’ve heard.

One reason the software sounds so analog is that it models minute variations between voices. It does that by introducing subtle differences in values for pitch, pulse width, filter cutoff, envelope segments, portamento time, and many other variations that hardware would exhibit. You can even specify how far these values may deviate from one another.

Another reason is that such obvious care has gone into duplicating the raw waveforms and filter characteristics of hardware as closely as possible. When I listen to naked waveforms from the VCOs and compare them to the same from my 2600 M, they sound incredibly close. And when I duplicate the software’s factory sounds on my 2600 M, as long as they don’t require features the hardware doesn’t have, they can sound remarkably close too. I couldn’t ask more from a software emulation of synth hardware.

Now what would you pay?

Compared with ARP 2600 hardware and even with competitors’ ARP 2600 emulations, Korg’s software offers a ton of extras. It has everything the hardware has and a whole lot more. Standout extras include the SEM-like Mode-Sweep filter, the DAHDSR envelope, and two bonus LFOs. I haven’t even mentioned key transposition, set lists, or the ability to retune individual notes and choose from a list of preprogrammed 12-note scales.

My only real gripe is that so many controls are crammed into the available onscreen real estate on the Main panel that it can be difficult to view everything clearly. I wish you could zoom in and expand specific sections as you can with Cherry Audio’s Rhodes Chroma software, for example. You can make ARP 2600’s  GUI bigger, but you still can’t scroll down to see more. The workaround I found is to use the zoom function in the Mac’s accessibility preferences when needed.

It certainly doesn’t help that most of the slider caps are black on a dark-gray background, but at least each has a tiny white stripe, unlike on the 2600 M, which I often need a reading lamp to use. If the slider caps were brightly colored like on the Behringer 2600, it would be easier to determine their positions at a glance.

My favorite use of this virtual 2600 is as a companion to the 2600 hardware. I create patches on the hardware and then reproduce them onscreen and save the patch so I can re-create it on hardware. There’s also a lot to learn from the excellent presets that talented sound designers have created in software by reproducing them in hardware.

I couldn’t be more pleased with ARP 2600 for Mac & PC, even though visibility may occasionally be challenging. It’s resource-hungry, but if your computer is recent enough to handle the load and you’re looking for realistic analog sound in a soft synth, you’ll unlikely do much better anywhere. If you want to verify my findings for yourself, download the free demo from Korg’s website.