MIDI Adapters

The main types

Bluetooth MIDI (DIN)

— Two 5-pin plugs on a short lead or a stub – one goes in MIDI OUT, one in MIDI IN – and the adaptor draws its power from the MIDI OUT socket, so there is nothing else to plug in. CME WIDI Master, Roland WM-1, Yamaha MD-BT01.

Bluetooth USB host

— For keyboards that only have a USB socket. The adaptor is the 'computer' the keyboard thinks it is talking to, and it forwards everything over Bluetooth. Needs its own power, usually USB-C. CME WIDI Uhost, Yamaha UD-BT01.

USB dongle

— Goes in the computer end and gives it a dedicated, low-latency Bluetooth MIDI port. Mostly a Windows thing – macOS and iOS have decent Bluetooth MIDI built in – but even on a Mac a dongle from the same family as the keyboard adaptor is the more reliable pairing. CME WIDI Bud Pro, Roland WM-1D.

USB MIDI host (wired)

— A box that turns a USB-only controller into 5-pin DIN in and out, no computer needed. On its own it is a wired product, but with a DIN Bluetooth plug on the back of it a USB keyboard goes wireless. Kenton MIDI USB Host.

Thru / merge box

— One MIDI source to many destinations (thru) or several sources into one (merge). The Bluetooth versions let one wireless keyboard drive a whole rack of hardware.

Jargon

Central and peripheral

— Bluetooth LE's two roles. The peripheral advertises ('I'm a MIDI keyboard'); the central finds it and connects. Phones and computers are always centrals. A plain adaptor like the Yamaha MD-BT01 is only ever a peripheral, so two of them cannot talk to each other – you need a computer or phone in the middle.

Pairs without a computer

— Adaptors that can play either role, so one can be the central for another. This is what lets a WIDI Master in a keyboard talk straight to a WIDI Master in a synth module. Look for it if you want a wire-free link between two pieces of hardware.

Group pairing

— One central connecting to several peripherals at once – CME's WIDI range does one-to-four – so one keyboard can drive up to four wireless modules, or one box can collect four wireless controllers.

Latency

— The delay between pressing a key and the note arriving. Bluetooth 5 adaptors quote around 3 ms, which is less than the distance between you and a stage monitor. Bluetooth 4 adaptors and phone Bluetooth stacks can be 10–20 ms, which good players notice on fast parts.

Range

— Quoted in open air; walls and bodies cut it. 10–20 m is normal, which covers a stage but not a stadium. Roland's Fast Mode and similar shorten range in exchange for lower latency.

Bus power

— MIDI OUT sockets carry a few milliamps, which is enough to run a DIN adaptor. USB-host adaptors have to power the keyboard as well as themselves, so they need a proper USB supply.

Class compliant

— A USB MIDI device that needs no driver. Every USB host adaptor requires this; almost every controller made in the last fifteen years is.

Choosing

Look at the socket on the keyboard first. DIN in and out: a DIN adaptor. USB only: a USB host adaptor. Both: DIN is simpler, because it is powered from the socket.

Decide what the other end is. A phone or Mac needs nothing extra. A Windows PC wants a dongle. Another piece of hardware needs an adaptor at each end and both must be the kind that pairs without a computer.

For a band rig – a satellite keyboard playing a synth or laptop across the stage with no cable – stay inside one brand's family; CME's WIDI range pairs with itself most reliably and its app lets you fix pairings so they reconnect on power-up. The wire-free keyboard guide walks through the whole setup, including running the keyboard from a power bank.