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Understanding MIDI Basis for your Stompboxes

Understanding MIDI Basis for your Stompboxes

What is MIDI? Behind this term lies an innovation that has revolutionized the world of musical instruments. However, this designation can also evoke apprehension because what it encompasses remains largely unknown to most musicians. In this blog series, we will shed light on how MIDI works so that you'll never fear plugging in a MIDI cable again and can fully harness everything it offers for your musical creations.


Episode 1: What is MIDI?

In this first article, we will explore what MIDI is and how it emerged in the 1980s with the rise of electronic music and the democratization of computing.  



MIDI stands for "Musical Instrument Digital Interface." It is a digital communication protocol that allows musical instruments to communicate with each other. Wi-Fi, Ethernet, and USB are other examples of communication protocols we use every day, adapted for broader purposes than just music.

 In the 1980s, with the increasingly widespread use of synthesizers, an idea emerged among iconic manufacturers of the time such as Roland, Sequential Circuit, MOOG, and others: the idea of connecting multiple devices such as keyboards, drum machines, sound generators, or computers to interact with each other. The goal was notably to control multiple sound generators from different brands with a single keyboard and to connect the latter to a computer to record the notes played by the musician and replay them later, varying the tempo, for example. This new invention is intended to replace the rudimentary 'CV gate' system that has been used up until now.

Dave Smith with the Prophet 600 synthesizer in 1982 was the first to commercialize an instrument using this standard.


Fig. The CV gate on the original PROPET5 was replaced in 1982 by the first MIDI connections on the prophet 600. 


Hardware connections 

But how do you make two musical instruments communicate? Let's take the simple example of a master keyboard connected to a sound generator. Physically, you first need to connect the master keyboard from its MIDI OUT connector to the MIDI IN connector of the generator using a MIDI format cable. Most devices with MIDI also have a MIDI THRU connection, allowing you to connect multiple devices in series. The standard connector used for MIDI is the 5-pin DIN. There are also MIDI TRS format cables available today, which will be described in more detail in a future blog post. Fig. Some devices have all 3 MIDI sockets, in, out and thru. Other devices, such as the Kernom Ridge, have one input and one output, which can be configured as either OUT or Thru, to save space. 


Fig. MIDI Cables can be DIN5 on the left, or minijack TRS on the right


The MIDI Protocol

 MIDI relies on digitally encoded messages that a transmitter sends to a receiver capable of decoding and interpreting them. For two instruments to interact, they must speak the same language. The MIDI standard, defined by the MIDI Association (, establishes this language so that all manufacturers can design devices capable of emitting or interpreting MIDI messages.

 Let's take the simple example of a master keyboard: when a musician presses a key on a keyboard, a MIDI message is sent by the keyboard, encoding the number of the pressed key. With a grand piano keyboard having a maximum of 88 keys, the MIDI standard numbers the musical notes from 0 to 127. For example, the number 60 is assigned to the middle C on a piano keyboard, 61 being the adjacent C sharp, 62 the D, and so on. Similarly, the velocity at which the note was played is also encoded from 0 to 127, with 0 representing the slowest velocity and 127 the fastest. The sound generator receives this message, decodes it, and can then generate a sound corresponding to the played note, while adjusting the tone to the velocity of play.

 The musician can also turn a volume potentiometer on their keyboard. A MIDI message is sent to indicate that the volume should be adjusted, along with the value of the potentiometer. The minimum volume is encoded by the number 0 and the maximum volume by the number 127. The generator then adjusts its output volume after decoding this message.


MIDI Channels

To facilitate the connection of multiple devices, the MIDI protocol offers the option to select one of the 16 available transmission channels. Each receiver only receives messages transmitted on the channel to which it is assigned.It's a bit like a postal address; we only receive the letters that are addressed to us. Let's take the example of the master keyboard: we can configure the notes to the left of middle C to be sent on channel 1 for a bass sound, while those to the right are sent on channel 2 for a piano sound.

By connecting two generators in series (MIDI out connection from the keyboard -> MIDI input of generator 1, MIDI THRU output of generator 1 -> MIDI input of generator 2) and setting generator 1 with bass sound to MIDI channel 1, only the notes played below middle C will be reproduced by this generator. By adjusting generator 2 with a piano sound  to MIDI channel 2, only the notes played above middle C will be supported by this generator


Fig. Devices connected in series 


MIDI Messages

Each MIDI message begins with the channel number on which it should be interpreted, followed by the type of information transmitted (note played, volume adjustment, etc.) and the corresponding values (note number, note velocity, volume value, etc.).

In addition to simple data such as played notes, MIDI incorporates other types of messages, such as control change (such as adjusting volume) and program change (to recall a preset on a device, similar to how a TV remote recalls a specific channel), as well as special messages like SysEx (system exclusive) for transmitting more complex data, such as updating a device.

There are also MIDI clock messages which synchronize the playback of multiple drum machines or sequencers at the same tempo, as well as varying the tempo synchronously across all devices simultaneously.

Fig. MIDI can be used to design many controllers, such as a fader box or MIDI footswitch like the Morningstar Engineering MC6 Pro , that can add new controls to your stompbox.


Today and Tomorrow

What's fascinating is that the MIDI format remains optimal for most musical needs even today and remains the most widely used standard for connecting electronic instruments. Many manufacturers, such as Ableton, Native Instruments, Korg, Focusrite, and even Apple, have joined the MIDI Association as partners, and new message types, such as MPE, have been added since 1982. Updates to the MIDI format have also been introduced to make it compatible with USB, Wi-Fi, and Ethernet. Nevertheless, the message format has remained the same since the beginning, demonstrating the quality of design of this format by the original designers, who carefully considered the needs of musicians and clearly envisioned possible evolutions in music. Fig. Futuristic controller like the Embodme erae touch can provide a novel approach to control your pedal via MIDI.


Next blogs

After browsing the MIDI history and its basic concepts, we will delve into more detail in future posts on certain specific message types, such as Program Changes, providing more specific usage examples for effects like the RIDGE overdrive or the MOHO fuzz. We will also explore how to use a MIDI switcher (also called controller) to load presets on multiple pedals at once.


Photo de l'auteur

by Antoine Petroff

Antoine is a seasoned audio, electronics and acoustics engineer with 20 years of experience both in the studio and in the lab working on high end audio products. He also plays keyboard and guitar and therefore has both a deep technical and artistic understanding of today’s musicians’ needs.

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