What does it mean when it says use device as MIDI?

MIDI stands for Musical Instrument Digital Interface. It is a technical standard that describes a communications protocol, digital interface, and electrical connectors that connect a wide variety of electronic musical instruments, computers, and related audio devices for playing, editing and recording music. https://en.wikipedia.org/wiki/MIDI

The MIDI standard was published in 1983 by music industry companies to allow different digital instruments and other devices to connect and communicate with each other. https://www.merriam-webster.com/dictionary/midi The goal of MIDI was to establish a compatible standard for electronic music and musical instrument equipment to easily connect and communicate, regardless of manufacturer or type of instrument/device.

MIDI Basics

MIDI stands for Musical Instrument Digital Interface. It is a technical standard that describes a protocol, digital interface, and electrical connectors that connect a wide variety of electronic musical instruments, computers, and related audio devices for playing, editing and recording music (Source 1).

The key thing that distinguishes MIDI from an audio signal is that MIDI does not transmit actual audio waveforms and frequencies. Instead, MIDI sends event messages such as note on/off, pitch bends, control changes etc. that control synthesizers, samplers, drum machines and other MIDI devices. This data is sent over a MIDI cable in the form of digital data. The receiving MIDI device converts this data into musical sounds (Source 2).

So in summary, MIDI itself does not make any sounds. It simply sends digital data that triggers the receiving device to play the appropriate sounds. This is different from an audio signal which transmits the actual audio waveforms.

Using Devices as MIDI

The term “Use device as MIDI” refers to using a device like a smartphone, tablet, or audio interface as a MIDI controller or interface. This allows the device to send and receive MIDI data to/from other hardware and software.

When a device has a “Use as MIDI” mode, it means the device can function as a MIDI controller by transmitting MIDI data from its touchscreen, buttons, knobs, faders etc over its USB or other connection. For example, synthesizer apps on a phone or tablet could allow using the touchscreen as a MIDI controller for external hardware synths.

Similarly, a device like an audio interface with this mode enabled can function as a MIDI interface, allowing MIDI data to be sent between the computer and external MIDI gear. The interface converts the MIDI data to and from the USB connection.

Enabling “Use device as MIDI” essentially turns the device into a MIDI controller or interface to integrate with a MIDI system. This allows musicians to control MIDI software and hardware using the interactive features of these devices.

MIDI Controller Devices

MIDI controller devices allow musicians to send MIDI performance data to external devices like synthesizers, DAW software, lighting rigs, and more. Some common examples of MIDI controller devices include:

MIDI keyboard controllers – These keyboard controllers connect to a computer via USB or MIDI cables to control virtual instruments and DAW software. Popular options include the Akai Professional MPK Mini MKIII, Novation LaunchKey Mini MK3, and Nektar SE25.
Drum pad controllers – These devices contain velocity-sensitive drum pads for finger drumming and triggering samples. Examples include the Akai Professional MPD218 and Alesis SamplePad Pro.

MIDI guitar controllers – These allow guitarists to control MIDI using their traditional guitar playing technique and convert the audio signal to MIDI data. The Roland GR-55 and the Fishman TriplePlay Wireless MIDI Guitar Controller are two options.
MIDI wind controllers – These convert wind instrument audio into MIDI data to control synths and samplers. The Akai EWI and the TEControl BBC2 breath controller are popular picks.
MIDI DJ controllers – DJ’s use these devices with DJ software to mix tracks and control elements like loops, samples, and effects. Common options include the Pioneer DDJ-SB3 and the Numark Mixtrack Pro III.

The above covers some of the most common types of MIDI controller devices musicians use to generate MIDI performance data and control external sound sources.

MIDI Interface Devices

MIDI interface devices allow you to connect MIDI devices like keyboards, drum machines, and sequencers to your computer. This enables you to use your computer as a central hub for your MIDI setup.

Many audio interfaces designed for music production include MIDI input and output connections alongside the audio inputs and outputs. For example, the M-Audio AIR 192|6 is a 2-in, 2-out USB audio interface that also provides MIDI I/O.

Using an audio interface with built-in MIDI ports allows you to connect MIDI gear directly to the interface via 5-pin DIN cables. The MIDI data can then be sent to music production software on the computer via the USB or Thunderbolt connection.

Some external USB or Thunderbolt sound cards also offer MIDI ports along with high-quality audio conversion. For example, the Focusrite Scarlett 2i2 is a popular entry-level interface with MIDI input and output.

Using a dedicated audio interface with MIDI connectivity allows you to connect all your studio gear digitally via one hub while taking advantage of professional quality audio conversion and low-latency monitoring.

Computer as MIDI Device

Your computer or digital audio workstation (DAW) software can act as a MIDI device to send and receive MIDI data. This allows you to use MIDI controllers and instruments with your DAW without needing a separate MIDI interface device.

To setup your computer as a MIDI device:

On Windows, open the Device Manager and enable the Microsoft GS Wavetable Synth under Sound, video and game controllers. This will allow your PC to act as a MIDI synth.

On Mac, open Audio MIDI Setup in Applications > Utilities. Click on Window > Show MIDI Studio to view available MIDI devices. Click + to create a new external MIDI device for your computer.
In your DAW, enable MIDI input and output from your computer/soundcard. This allows routing of MIDI data between your controllers/instruments and the DAW.
Set the MIDI channel on your controllers and DAW to match. This ensures they communicate on the same channels.

Once setup, your DAW will appear alongside your other MIDI gear. You can use it to send MIDI data to external devices to control parameters and playback. It will also receive MIDI from controllers which can be recorded and edited.

Using your computer as a MIDI device allows seamless integration between your DAW, instruments and controllers. It removes the need for a dedicated MIDI interface unit in basic setups. Most DAWs include MIDI routing capabilities to handle MIDI I/O between software and hardware.

MIDI Cables and Connections

There are several types of cables that can be used to connect MIDI devices:

Standard MIDI cables – These use 5-pin DIN connectors and carry MIDI messages. They are the most common cables used to connect MIDI gear.
USB cables – Many MIDI controllers and interfaces connect via USB. Standard USB printer cables can be used.
TRS (Tip Ring Sleeve) cables – Some devices use 1/4″ TRS connections for MIDI. There are two types of TRS MIDI cables, referred to as Type A and Type B, which are wired differently.

XLR cables – MIDI can also be transmitted via standard XLR mic cables. This is less common but works over short distances.

The most important factors when selecting a MIDI cable are using the proper connectors for your devices and ensuring the cable carries MIDI signals. As noted in this Perfect Circuit article, it’s recommended to use dedicated MIDI cables when possible.

MIDI Channels

MIDI utilizes 16 channels for sending and receiving data between devices. Each MIDI channel acts as a separate stream of MIDI messages. This allows multiple devices to communicate over a single MIDI cable while keeping the messages separate.

For example, a MIDI keyboard could send note data over channel 1, while a drum machine sends rhythm data over channel 10. The receiving device listens on the appropriate channel to receive the corresponding messages. Both streams of MIDI data can be sent over the same cable without interfering with each other.

MIDI channels are numbered 1-16. Channel 1 is the default channel on most devices. Devices can be set to transmit on a specific channel, and listen/receive on a specific channel. This allows routing MIDI data from one device to another as needed. Using multiple channels enables complex MIDI setups and workflows.

Using MIDI Data

MIDI data can be used for a variety of creative and production purposes in music and audio. Here are some of the main ways MIDI data is utilized:

Sequencing – MIDI data can be recorded, edited, and played back in sequencer and digital audio workstation (DAW) software to create full compositions and arrangements. MIDI sequencing allows for easy editing of notes, rhythms, chords, and more.

Controlling instruments and hardware – MIDI data can control synthesizers, samplers, drum machines, and effects units, directing them to play notes and change parameters in real-time. This allows MIDI data to trigger and manipulate sounds and effects.

Notation and scoring – MIDI data can be imported to notation software like Finale or Sibelius to generate musical scores and sheet music automatically.

Automation – In a DAW, MIDI data can automate parameters like volume, panning, effects, and more on audio tracks for mixing. MIDI automation allows dynamic changes to sound as the music plays.

Analysis – MIDI files can be loaded into musical analysis software to study the melodies, harmonies, rhythms, and structure of the contained music.

Storage and transfer – MIDI files are a compact way to store musical compositions and songs in a universal format for transfer between different programs and platforms.

Live performance and sound triggering – MIDI messages can be assigned to trigger audio samples and effects in real-time during live performance or music production.

As you can see, MIDI data has many creative uses for writing, editing, analyzing, storing, controlling, and manipulating music (https://archive.org/stream/mac_The_Audible_Macintosh_1992/The_Audible_Macintosh_1992_djvu.txt). The potential applications are nearly endless.

Conclusion

MIDI, or Musical Instrument Digital Interface, is a protocol that allows electronic musical instruments and other devices to connect with each other. Using devices as MIDI controllers or interfaces allows musicians to control parameters in music software and hardware using external devices.

Some key points:

MIDI controller devices like keyboards, drums, guitars can be used to play and control virtual instruments and effects in a DAW or other music software.
MIDI interfaces allow MIDI devices to connect to computers via USB or other connections.

Computers themselves can serve as powerful MIDI controllers when using MIDI-mapping in DAWs.
MIDI cables and proper setup of MIDI channels between devices is important for routing MIDI data.
MIDI data contains performance information like notes, controller messages, tempo, etc. that can control parameters in other MIDI devices.

With the proper hardware and software setup, using devices as MIDI provides musicians with flexibility and control in music production.