Introduction
In this article, I want to discuss the significance of CVs (control voltages) and MIDI (Musical Instrument Digital Interface) from the standpoint of a practical musician. We all know MIDI, to some extent. Some know it as a means to generate “MIDI sounds,” from simple beeps and noises to pianos, strings, guitars, and drums. But more accurately, MIDI is a digital control protocol—it tells gear what to do but carries no audio. CVs, on the other hand, are probably lesser known. Essentially, CV is MIDI’s analog counterpart: CVs are an analog control protocol—they tell gear what to do but carry no audio.
TL;DR — Why CV and MIDI matter: You don’t need to be a tech to use this stuff. CV is the hands-on part—you turn a knob and, a voltage sweeps a filter or bends a note. MIDI is the common language—every keyboard, DAW, plugin, and a lot of modern effects devices speak it. Put them together and your pedals, synths, and workstation behave like one coherent, integrated instrument. You are in control.
CVs
CVs predate MIDI by decades. Similar to MIDI, they are used to control analog synthesizers. Beyond oscillator pitch control, they were also used to modulate parameters such as volume, tone, and timbre. This gave musicians expressive, dynamic control over the shape and character of the synthesizer’s sound.
The underlying beauty of CVs is that they are simply signals, just like audio. CVs are typically low-frequency signals that extend all the way down to DC and can be generated in various ways. The most basic CV is produced by a potentiometer that forms a voltage divider: for example, one leg is connected to GND (0 V), the other to +5 V, and the wiper (the middle leg) varies from 0 V to +5 V as you turn the knob. Beyond simple front-panel knobs, joysticks, pitch wheels, and modulation wheels are also built from potentiometers acting as voltage dividers.
Those who are familiar with wiring electric guitars will quickly notice the similarity with the way volume pots are wired — except that instead of connecting source to the pickup output, you connect the source to a fixed 5 V DC voltage. It’s as simple as that: you have a CV potentiometer. That output can control just about anything, right at your fingertips.
There are many ways to generate CVs, and the analog synthesizer keyboard is a very visible example. In the 1960s, Bob Moog established the 1 V/octave convention, where 1 V represents an octave. These keyboards output CV signals that vary with each key pressed. Beyond keyboards, devices such as envelope generators, sequencers, and other controllers also produce CVs. The possibilities are wide-ranging.
If you are a modular synth aficionado, you already know what I’m talking about. For the practical musician, the details aren’t necessary. My point is that all these mechanisms from the world of synthesizers can be applied in ways you might not expect — and they can be surprisingly useful, even outside the world of synthesis.
MIDI
And now we have MIDI. We’ve had it since the 1980s, when it was developed as a lingua franca among synthesizers. Beyond a certain complexity, analog CVs couldn’t keep up. If you’ve seen how monophonic modular synthesizers are wired (image above!) using patch cables that carry CVs — tangled into a snake pit of cables — imagine the complexity of a polyphonic analog synthesizer, where instead of one note at a time, you can play chords. Suddenly, the complexity multiplies by the number of notes you play simultaneously: polyphony. That’s what lay inside complex analog polyphonic synthesizers of the era, hidden behind the front panel. It quickly became untenable — and prohibitively expensive.
MIDI is comprehensive. It defines standardized Channel Voice messages such as note on/off, velocity, polyphonic aftertouch and channel aftertouch, control change (CC), program change, and pitch bend, along with System messages for clocking, song position, and exclusive data. Continuous control is 7-bit, with support for 14-bit high-resolution CC (via MSB/LSB pairing) and 14-bit pitch bend. MIDI supports 16 channels, allowing multiple instruments to be addressed independently. MIDI is transport-agnostic: while the original 5-pin DIN runs at 31.25 kbps, USB, Ethernet, and wireless links allow much higher data rates.
MIDI 2.0 was ratified in 2020, extending the original 1.0 spec by leaps and bounds. To keep it simple, we will not discuss it here. MIDI 1.0 is more than sufficient for most practical use cases.
MIDI CCs
MIDI Continuous Controller (CC) messages are used to send real-time control data, including sliders, knobs, pedals, LFOs (Low Frequency Oscillators), and envelopes. Think of it as CVs supercharged. Instead of having one wire per CV, you have a multitude of control signals carried over a single MIDI cable. What once required a snake pit of cables is now reduced to a single connection. You have 16 channels, and each channel can carry a wide range of controller information, including modulation, volume, pan, expression, sustain, resonance (timbre), and brightness (filter cutoff), just to name a few.
For the purpose of CV to MIDI, we will focus only on MIDI CCs, although other MIDI messages such as pitch bend and program change are also worth including in the discussion.
Example Use Cases
- MIDI CC1 (Mod Wheel) → Depth of modulation
Roll in a touch of vibrato or tremolo on sustained notes. - MIDI CC7 (Channel Volume) → Level rides
Smoothly fade parts up or down. - MIDI CC11 (Expression) → Drive or tone morph
Control gain or wave shaping — sweep from clean to edge-of-breakup, or brighten and darken the tone. - MIDI CC (assignable) or MIDI Pitch Bend → Pitch shift
Bend notes and chords: from vibrato-like shimmer to dive bombs, glides between chords, or shifting whole phrases up or down. - MIDI CC74 (Brightness) → Filter cutoff
Sweep a low-pass filter for wah-like sweeps, from muted to wide open.
Expression Pedals
Chances are, you’re already using a CV device without realizing it. In fact, modern expression pedals are CV devices. At their core, expression pedals are just passive voltage dividers: the potentiometer splits the host’s reference voltage against ground, and the wiper — the middle terminal — becomes the control signal.
The problem is the lack of standardization. The two most common wiring conventions are:
- Korg/Yamaha: tip = wiper, ring = +V reference, sleeve = ground.
- Roland/Boss: tip = +V reference, ring = wiper, sleeve = ground.
Although many devices accept either wiring type, there is no standard reference voltage. Some use 5 V, others use 3.3 V. This means you cannot safely plug CV into an expression input unless the documentation explicitly allows it. Some manufacturers, such as Electro-Harmonix (EHX), clearly document when CV is allowed, often stating 0–5 V CV via a TS plug, with the ring carrying the pedal reference. Others provide similar specifications — always check your device’s manual to be sure.
In recent years, many guitar effects have added CV inputs—showing up on delays (Electro-Harmonix DMB/DMTT, Toneczar Echoczar, Line 6, Strymon), tremolo (Goatkeeper), flangers (Foxrox Paradox), filters/envelope and ring-mod units (Big Briar/Moog, WMD), and even distortion (WMD). Implementations vary, so check each maker’s spec before patching. (Source: Wikipedia — CV/gate)
So what’s the relevance of all this? For starters, you are not limited to using expression pedals. You can, for example, wire a potentiometer into your guitar and use it as an expression input. Beyond that simple “hack,” you can also explore specialized CV controllers, such as an electronic whammy bar or a ribbon controller.
If the target device you want to control supports CV, or its TRS expression jack is documented to match your source (voltage range, reference voltage, polarity), just control it directly; MIDI conversion isn’t required.
CV to MIDI
If injecting a control voltage into your precious gadget sounds too scary, a safer alternative is to convert the CV to MIDI. Many modern devices accept MIDI, and since MIDI is universally adopted, you can control just about anything — from floor or rackmount effects to DAWs.
There are a few off-the-shelf CV-to-MIDI devices available on the market. In this section, we’ll take a look at some examples.
CV to MIDI isn’t magic; it’s plumbing. The real question is how well a device can read your voltages and translate them into MIDI. This is a practical look at off-the-shelf gear, with a focus on controller use rather than CV/Gate keyboards. Specifications are taken from manufacturer documentation, with commentary on usability and workflow.
Method & limitations: This is a desk review, not a hands-on test. Everything here is based on published manuals, product pages, and maker documentation available at the time of writing. Specifications may change, and firmware often evolves. Treat this as a curated overview of the options, then verify details against the latest manuals when you buy.
At a Glance
| Product | Format | CV inputs | Resolution | Stand alone? |
| Audiofront MIDI Expression (single) | Desktop USB | 1 | 14 bits | No (USB host) |
| Audiofront MIDI Expression Quattro | Desktop USB | 4 | 14 bits | No (USB host) |
| Audiofront MIDI Expression iO | Desktop USB + DIN | 4 | 14 bits | Yes (9 V + DIN) |
| Befaco VCMC | Eurorack | 10 | 14 bits | Yes (in rack) |
| Befaco CV Thing | Eurorack | 8 | 14 bits | Yes (in-rack) |
| Doepfer Pocket Electronic (PE) | DIY board | 16 | 7 bits | Yes (board with MIDI) |
| Doepfer Wheel Electronic (WE) | DIY board | 4 | 7 bits | Yes (board with MIDI) |
Audiofront — MIDI Expression family (single • Quattro • iO)
Designed for TRS expression jacks; no special interfacing. Inputs read 0–3.3 V. Assign to CC/NRPN (up to 14-bit) or pitch bend (14-bit). Setup: set min/max, choose a curve, optional center-deadband, save preset. Pedal sensing auto-detects expression/sustain/hi-hat/dual-switch types and loads a preset; polarity options cover Roland/BOSS vs Korg/Yamaha wiring.
- MIDI Expression (single): one input over USB.
- Quattro: four inputs over USB.
- iO: four inputs plus DIN, true standalone on 9 V.
CC-capable inputs: single: 1 • Quattro: 4 • iO: 4
MIDI I/O: single/Quattro = USB; iO = USB + DIN
Pros. Multiple models; documented pinouts; supports 14-bit output; iO adds DIN and standalone.
Cons. single/Quattro require a USB host; 1 or 4 inputs only.
Befaco—VCMC & CV Thing (shared core, two formats)
Same core, two formats. VCMC is the performance surface with eight 60 mm faders, buttons, and extra I/O; CV Thing keeps the mapper and drops the big surface. Per input you select 0–5 V or 0–10 V, set scaling/limits/curves, and map to CC (7-/14-bit), NRPN (7-/14-bit), pitch bend (14-bit), or notes. MIDI goes out over USB and DIN on VCMC, and USB plus TRS-MIDI on CV Thing. CV Thing is based on VCMC (shared code), so behavior and high-res modes match.
- VCMC: 10 CV inputs (8 main + 2 aux), 8 gate inputs; MIDI over USB and DIN-5; eight 60 mm faders with buttons.
- CV Thing: 8 CV inputs; MIDI over USB and TRS-MIDI (DIN adapter typically included); compact format.
CC-capable inputs: VCMC 10 • CV Thing 8
MIDI I/O: VCMC = USB + DIN-5 • CV Thing = USB + TRS-MIDI
Pros. Shared flexible engine; supports 14-bit control; per-input range selection; multiple MIDI outputs; long-throw faders provide tactile control on VCMC.
Cons. VCMC takes space.
Doepfer — Pocket & Wheel Electronic (PE/WE)
DIY MIDI controller cores with simple, predictable behavior. Old-school DIP-package microcontroller design; continuous data is limited to 7-bits.
PE has 16 analog inputs (0–5 V) that can be mapped to MIDI events such as CC, pitch bend, or aftertouch. It seems reliable and inexpensive.
WE has 4 analog CV inputs (0–5 V) plus 1 switch. A built-in center “plateau” (deadband) holds pitch-bend at zero around mid-travel, and a reduced-span jumper rescales short-throw sensors to use the full MIDI range. Scan rate ≈ 50–60 samples/s (~20 ms). Continuous data are 7-bit; if you assign pitch-bend it’s sent as 14-bit on the MIDI wire, though the source granularity remains 7-bit.
- CC-capable inputs: PE 16 • WE 4
Pros. Low cost; PE offers 16 assignable CV inputs; WE adds center-plateau and reduced-span for wheels/joysticks; documentation is straightforward.
Cons. Continuous controls are 7-bit; WE scans at ~50–60 samples/s (~20 ms); supplied as bare boards (you provide enclosure/wiring).
Related: keyboard centric CV/Gate→MIDI (brief)
These converters are designed primarily for CV keyboards: they turn pitch CV plus gate into MIDI notes and offer limited continuous control on a small number of inputs. They’re effective for simple monophonic playing and wheel/joystick capture. However, they’re not included in the main comparison because this article focuses on controller-style CV→MIDI. These boxes provide multiple simultaneous CC/NRPN lanes for pedals, faders, sensors, and modular control.
Kenton Pro CV→MIDI (desktop): Monophonic
CV/Gate→MIDI with pitch bend on the wire; two Aux CVs can send CC. Main pitch A/D 16-bit; Aux A/D 12-bit. Good for converting a CV keyboard or wheel to MIDI, but limiting if you need multiple continuous controls.
Doepfer A-192-2 (Eurorack):
Two independent CV/Gate engines aimed at CV keyboards. Per engine: CVN/Gate/CVV/CVC (note, gate, velocity, one CC lane). Across the module that’s two CC lanes total; CC 7-bit, PB 14-bit. Suited to note/velocity conversion rather than broad CV control.
Throughput & scan rates (why some boxes feel smoother)
DIN MIDI is 31.25 kb/s. A 3-byte Channel Voice message with framing is ~30 bits, so the upper bound is about 1,000 messages per second per port (higher with running status). USB-MIDI has far higher throughput—the bottleneck is usually the converter’s scan/update rate, not the link. Modern designs manage hundreds of hertz to kilohertz per lane; 50–60 Hz is slow by today’s standards and will show stepping on fast or wide moves. For smooth control, prefer devices that publish high per-lane scan/update rates and support 14-bit paths (pitch-bend and CC/NRPN via MSB+LSB).
I use Expert Sleepers’ excellent ES-9 audio interface with Ableton’s CV Tools pack to send envelopes, LFOs waveforms, and gates to various modules. This is how I add dynamic range to my guitar robot picking. The robot always picks at the same speed, which means that every picked note is roughly the same volume–so I need to control amplitude some other way. The setup is about the same for VCV Rack.
The CVs come out of the ES-9 to VCA/VCFs, and the outputs of those modules–which get their audio input signals from my Nexus breakout box–go back to the ES-9 and into the DAW. Each string gets its own signal processing chain. Since the robot is triggered by MIDI sequences, the same notes and their velocities can control the analog modules.
You can see a picture of the setup in this video:
(You already know this, but I thought it might be useful for others.)
Splendid! That’s an interesting way of extracting CVs!
When I was first testing out the feasibility of the project I am … still .. working on (a digitally pitch-shifted pedal steel guitar), I used a couple of the early Nu pickups and sent the signals to separate channels in Logic Pro via an audio interface. I had a pot sending CV to an Arduino which I had programmed to convert to 14-bit MIDI messages. These I sent to separate plugins in Logic Pro (one on each channel). And poof, the first proof of concept. 2014.
Wow! 2014. How time flies fast, Alan!
The Ardiino does not have 14-bit converters, though, right?
Note that the Audiofront Quattro and single channel cv to midi converters DO function standalone . You simply program them with a usb connection to a computer, and then you can either use them with our without a computer by powering them via usb. Of course, the usb midi out doesn’t work when run like this as it’s connected to only a usb power supply – but the 5 pin MIDI does function as a perfectly fine output.
That’s good to know. As mentioned, this is a desk review, not a hands-on test.
Wait, they don’t have MIDI 5-pin DIN out, do they?