2. Sending & Receiving MIDI

Sending and Receiving MIDI

In part 1 we covered what MIDI messages are, and what they do. In case it's been a while, here's a quick recap:

  • MIDI messages are numbered from 0-127, often with a value also set between 0-127
  • MIDI messages are kept separate between devices by giving each message a channel number from 1-16
  • MIDI connectors and Messages are used differently by some manufacturers and deviate from standard implementation
  • The most common MIDI messages are: Program Change (PC), Control Change (CC), Note On, Note Off, and the MIDI Timing Clock

In this lesson we're going to cover how these messages are sent and received. They're officially called MIDI Transports.

What is a MIDI Transport?

A MIDI transport is one of the ways that the MIDI specification allows for MIDI messages to be transmitted or received.

The list of MIDI transports given by the MIDI association is:

  • DIN5 Cable (Serial)
  • TRS Cable (Serial)
  • RTP (Typically Ethernet or other network connection)
  • USB
  • Bluetooth

Is MIDI Directional?

Being such an old protocol, MIDI was developed with hardware and processing power that was much slower and less capable than we are used to having today. MIDI via the traditional DIN5 and more modern (but still serial-based) TRS connectors is directional in 99% of cases. MIDI devices will have a MIDI In and/or a MIDI Out jack.

MIDI In and Out/Thru Jacks in DIN5 form factor

To connect one device to another, you must connect the MIDI Out jack of one device to the MIDI In jack of the other. The cable itself is not directional, but if you plug a MIDI Out into a MIDI Out, no messages will be sent between devices.

Bi-directional MIDI Connections

USB MIDI, RTP MIDI, Bluetooth MIDI, and some proprietary (and non-standard) MIDI implementations are bi-directional using a single connection. USB MIDI, Ethernet, Bluetooth, and devices from Strymon & Meris are bi-directional and will send and accept MIDI with a single connection.

Note: Strymon and Meris require their own special MIDI hubs to process the two directions MIDI is being sent on the same cable

MIDI Thru Connections

If you want to join multiple device to a single controller, you'll find that a lot of device account for this by including a MIDI In, and a MIDI Out. Sometimes the MIDI Out may be labelled Thru or Out/Thru. This indicates that that jack can pass messages directly from the MIDI In to the MIDI Out. Some devices may have this feature but have it turned off by default with an onboard setting.

Note: Remember that if you have a chain of devices all connected to a controller, you'll need to have all the devices listening to messages on a specific MIDI channel. If you don't keep messages on different channels, you could have device responding to messages that are not intended for them.

Important Notes About USB MIDI

USB MIDI is a powerful and convenient addition to any MIDI device. However, there is a limitation that many people do not understand at first. It is actually a limit of the USB side, rather than the MIDI side.

USB to MIDI adapters are cheap and plentiful - but if you want to go USB to USB - you may need another piece of equipment in between.

If you have a MIDI controller (like the BRIDGE6) and a MIDI pedal with a USB connector such as a Source Audio C4 synth pedal or a Zoom Multistomp pedal, you might be tempted to think you can connect a USB cable from your controller to your pedal. Unfortunately this usually isn't possible due to the fact that USB devices require a USB Host device as part of the way USB works. In normal USB life, you plug a device (mouse, keyboard, camera, flash memory) into a computer, tablet, or phone.

In this case, the computer is designed to power and to recognise the capabilities of the connected devices. With most USB MIDI devices, this is not a function they have. USB MIDI Host is a rare feature, but it is available in some external boxes you can put on your pedalboard, and in some more expensive MIDI controllers.

Important Notes About TRS MIDI

TRS MIDI is, unfortunately, one of the most fraught connections. TRS MIDI is used mostly on device manufactured after about 2010. The TRS connector has great pro's:

  • It's rugged
  • It's super abundant, and therefore cheap
  • It's easy to find a replacement in a pinch
  • It's compact and doesn't take up heaps of space, allowing for more compact devices

However, manufacturers started using TRS MIDI connectors before there was a specification from the MIDI association. This has led to at least 5 different types of TRS MIDI implementations.

Eventually the MIDI association defined a standard, but the main companies using different implementations didn't change them. This means that DIN5 to TRS MIDI hubs of all kinds now exist, but happily many of them allow you to switch each individual output to match the brand of the device you need to connect.

What are the different types of TRS MIDI connectors?

The common types are:
  • Type A (MIDI Standard)
  • Type B
  • Tip Active (Ring floating)
  • Ring Active (Tip floating)
  • Bi-directional (e.g. Strymon pedals)

Some MIDI cable manufacturers will specify the Type that they are made for, but it's always best to check and ask, if possible.

Another fact about effects pedals with TRS MIDI is that most do not have a MIDI Out option - only a MIDI In. This is another factor that may see you needing to use a TRS MIDI hub. If you have three pedals, and only one MIDI out from your controller, you're going to need to send the MIDI Out into a hub, and then go from the hub to the three pedals.

Important Notes About Bluetooth MIDI

Bluetooth MIDI is one of the most exciting innovations in MIDI in the last decade. Coupling Bluetooth MIDI with USB battery banks has meant that many small MIDI control rigs have been able to become completely wireless and portable.

MIDI, being simple (and old), is a very lightweight data stream. This means that even with the very limited bandwidth of Bluetooth, MIDI is speedy, reliable, and very useable. Latency is always a concern for musicians, but companies like CME have managed to create Bluetooth MIDI devices with such low latency that thousands of people are now comfortable using them not only for changing presets and control values (which are usually less vital from a latency perspective) but also for playing MIDI instruments like MIDI wind controllers and MIDI keyboards!

The WIDI Jack is abolsutely tiny and can power itself from the MIDI Out port!

For a live instrument player to use Bluetooth MIDI is both a technological triumph and real testament to the low latency that's been achieved.

CME manufacture WIDI (Wireless MIDI) dongles that power themselves from the MIDI out jack of your device. They have ones that connect straight into a DIN5 jack, ones that connect with cables so you can use adapters to connect any size of TRS or DIN5, and they've even created a USB host MIDI Bluetooth device.

Note: Devices from different manufacturers that have Bluetooth MIDI may or may not work together. It's worth searching forums and facebook groups to see whether it's possible to connect your different devices.

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