Many different "transports" can be used for MIDI messages. The speed of the transport determines how much MIDI data can be carried, and how quickly it will be received.
Each transport has its own performance characteristics which might make some difference in specific applications, but in general the transport is the least important part of MIDI , as long as it allows you to connect all the devices you want use!
5-Pin MIDI DIN
Using a 5-pin "DIN" connector, the MIDI DIN transport was developed back in
1983, so it is slow compared to common high-speed digital transports available
today, like USB, FireWire, and Ethernet. But MIDI-DIN is almost always
still used on most MIDI-equipped devices because it adequately handles
communication speed for one device. IF you want to connect one MIDI
device to another (not a computer), MIDI cables are still the best way
It used to be that connecting a MIDI device to a computer meant
installing a "sound card" or "MIDI interface" in
order to have a MIDI DIN connector on the computer. Because of space
limitations, most such cards did not have actual 5-Pin DIN connectors
on the card, but provided a special cable with 5-Pin DINs (In and Out)
on one end (often connected to the "joystick port"). All
such cards need "driver" software to make the MIDI
connection work, but there are a few standards that companies follow,
including "MPU-401" and "SoundBlaster". Even with
those standards, however, making MIDI work could be a major
Over a number of years the components of the typical sound card and
MIDI interface (including the joystick port) became standard on the
motherboard of most PCs, but this did not make configuring them any
Serial, Parallel, and Joystick Ports
Before USB and FireWire, personal computers were all generally equipped with serial, parallel, and (possibly) joystick ports, all of which have been used for connecting MIDI-equipped instruments (through special adapters). Though not always faster than
MIDI-DIN, these connectors were already available on computers and that made them an economical
alternative to add-on cards, with the added benefit that in general
they already worked and did not need special configuration.
The High Speed Serial Ports such as the "mini-DIN" ports available on early Macintosh
computers support communication speeds roughly 20 times faster than MIDI-DIN, making it
also possible for companies to develop and market "multiport" MIDI interfaces that
allowed connecting multiple MIDI-DINs to one computer. In this manner it
became possible to have the computer address many different MIDI-equipped devices at the same time.
Recent multi-port MIDI interfaces use even faster USB or FireWire
ports to connect to the computer.
USB and FireWire
All recent computers are equipped with either USB and/or FireWire connectors, and these are now
the most common means of connecting MIDI devices to computers (using
appropriate format adapters). Adapters can be as simple as a short
cable with USB on one end and MIDI DIN on the other, or as complex as
a 19 inch rack mountable CPU with dozens of MIDI and Audio In and Out
ports. The best part is that USB and FireWire are
"plug-and-play" interfaces which means they generally
configure themselves. In most cases, all you need to do is plug in
your USB or FireWire MIDI interface and boot up some MIDI software and
off you go.
Current USB technology generally supports communication between a
host (PC) and a device, so it is not possible to connect to USB
devices to each other as it is with two MIDI DIN devices. (This may
change sometime in the future with new versions of USB). Since
communications all go through the PC, any two USB MIDI devices can use
different schemes for packing up MIDI messages and sending them over
USB... the USB device's driver on the host knows how that device does
it, and will convert the MIDI messages from USB back to MIDI at the
host. That way all USB MIDI devices can talk to each other (through
the host) without needing to follow one specification for how they
send MIDI data over USB.
Most FireWire MIDI devices also connect directly to a PC with
a host device driver and so can talk to other FireWire MIDI devices
even if they use a proprietary method for formatting their MIDI data.
But FireWire supports "peer-to-peer"
connections, so MMA has produced a specification for MIDI over IEEE-1394 (FireWire), which is available for download on this
site (and incorporated in IEC-61883 part 5).
If you are connecting a number of MIDI instruments to one or more
computers, using Ethernet seems like a great solution. In the MIDI industry there is not yet agreement on the market
desire for MIDI over Ethernet, nor on the net value of the benefits vs. challenges of
using Ethernet, and so there is currently no MMA standard for MIDI over Ethernet.
However, other Standard Setting Organizations
have specifications for MIDI Over Ethernet, and we think it appropriate that people know about
those solutions. There are also proprietary solutions for MIDI Over Ethernet, but because they are not
open standards they are not appropriate for discussion by MMA.
The IETF RTP Payload Format for MIDI
solution has received extensive modification in response to comments by MMA-members, and is also the foundation of Apple's own MIDI Over Ethernet solution. Though neither solution has been officially adopted or endorsed in any way by MMA, both technologies have stood up to MMA member scrutiny and so are likely to appear (in one manner or another) in future MIDI hardware and/or software products.
For the past several years, the IEEE has been developing
protocols for low-latency audio and video transport over Ethernet
with high quality of service. These protocols are known as
Audio/Video Bridging, or AVB, and are part of the larger IEEE 802.1
Working Group, which develops networking standards that enable
interoperability of such ubiquitous devices as Ethernet switches.
The AVB protocols provide precision time synchronization and stream
bandwidth reservation at the network level.
The AVB protocols do not provide a standard means for
interoperable communication of content such as a live video stream.
Utilizing the 802.1 AVB protocols, the IEEE P1722 AVB Transport
Protocol (AVBTP) draft standard provides the necessary content
encapsulation in an evolutionary manner by adopting the existing
IEEE 1394 (Firewire) audio and video streaming mechanisms already in
use by millions of devices. However, AVBTP is not limited to
bridging IEEE 1394 content, as it provides extensibility to
encapsulate new and different media formats.
The MMA collaborated with the IEEE P1722 working group to enable
transport of MIDI and any future content format defined by the MMA
over IEEE P1722 networks. The P1722 standard defines MIDI 1.0 content
within this protocol by referencing an MMA-authored document. The
MMA has not yet published that document, but plans to
do so in the near future.