MIDI interfaces are used as a link between electronic musical instruments, sound production devices and computer software, allowing musicians and producers to store, record and playback music with MIDI instruments and control devices. Keyboards and other instruments can control samplers and other sound modules and can input notation data to music scoring programmes via MIDI, and likewise, scoring programs and/or sequencing software can be used to play MIDI instruments directly without manual input.
Electronic musical instruments and devices were becoming increasingly common in the late 1970s, with early voltage-controlled analogue synthesisers. Manufacturers were able to use these voltage signals to link instruments together, but this proved inadequate for newer polyphonic and digital synthesisers. Some makers developed systems in order that their own equipment could be interconnected, but any one maker’s system was typically incompatible with all the others.
A universal synthesiser interface which would allow direct communication between equipment from different manufacturers was proposed in 1981, and over the next few years, this was modified by various companies and was renamed Musical Instrument Digital Interface, or MIDI. Public demonstrations followed in 1983, and the MIDI Specification was published later that year.
Choosing a MIDI Interface
Some keyboards and other instruments are designed with MIDI interfaces and USB functionality built in; if this is the case, an external interface will not be required. The owner’s manual or other maker’s documentation for the keyboard or instrument concerned should confirm whether or not this is the case. Most, but not all, MIDI interfaces are ‘cross-platform’ devices, which will work on all types of computers, whether Mac or PC. The description of any interface for sale should be checked, or the seller queried, to confirm this.
MIDI interfaces are generally fitted with even numbers of ‘ports’, i.e. the input and output sockets for connection to other equipment and would be referred to as 2-port, 4-port, etc. Each port can transmit up to 16 channels of MIDI data, and therefore, a 2-port could handle (2x16) 32 channels of data and an 8-port up to 128 channels. Many MIDI interfaces make provision for connection to other interfaces if more flexibility than this is required. The more advanced interfaces sometimes have the ability to synchronise to timing (clock) data from standalone recorders and video devices.
MIDI ports are labelled In, Out, and Thru in varying numbers on different devices. Basic controllers (keyboards etc.) might only have a MIDI Out, whereas the more advanced will have combinations of MIDI In, Out, and Thru. The In port receives MIDI data from a computer or other device, such as an interface, whereas MIDI Out is where data is transmitted to other devices. MIDI Thru passes out the same data as is present at the MIDI In. This allows daisy-chaining of a number of MIDI instruments and devices together to multiply their sound-making capability.
A recent innovation in this field is units which send MIDI data wirelessly, just as a wireless computer network or wireless microphone might do. These units have the obvious advantage of reducing wiring in the studio or music workspace, and the ability to alter the MIDI setup without unplugging and re-plugging cables. A wireless setup could even extend to having interfaces, recording devices, and computers in one room, and keyboards and sound modules in another, the obvious advantage to this approach being that the units with cooling fans and other noise-making elements can be isolated from rooms where quiet operation is required. Alternatively, units which require less frequent access can be removed to areas outwith the primary work area.
Many musicians and producers will work with MIDI instruments as well as conventional acoustic instruments and voices, and there are many choices of combined audio and MIDI interfaces. Selection of audio interfaces specifically could run to a whole article, but briefly, when looking at a combined audio/MIDI interface and considering the audio capability, the number and type of audio inputs should be examined in the same way as the MIDI ports to ensure that they meet current and future expansion requirements. Line-level inputs are appropriate for synthesisers, keyboards etc., microphone inputs are appropriate for voice and acoustic instruments, and some interfaces are fitted with so-called versatile inputs, those which are switchable for alternative uses. The number and type of audio outputs should also be considered for the purposes of monitoring or playback, and the more advanced audio interfaces will have digital input and output for connectability with digital recording and playback devices, such as hard-disk recorders and multi-track ADAT machines.
Some MIDI interfaces are intended specifically for certain instruments, notably those designed for use with guitars as opposed to keyboards. The majority of these are designed to use matching pickups which need to be installed on the guitar itself, and it will usually be self-evident that these are not intended for any other use. Early versions of guitar synthesiser systems were prone to tracking errors, and improvements have been made, but these types of controller still require an accurate level of playing. Other types of guitar interface function from the guitar’s standard output, and again, it should be clear that these are instrument-specific.
Lastly, MIDI interfaces come in different form factors, or casework styles. Some are designed to be freestanding, on a desktop or similar, some are designed to match with specific computers, and others are intended for rack-mounting. The choice will depend on the physical layout of the musician or producer’s studio or workspace, and either the overall size or the number of rack spaces required should be considered before making a purchase.
So, in broad summary, buyers should consider:
- Whether or not the instruments used have interface(s) built in
- The number of instruments and devices to be used
- If the interface is platform-specific (Mac or PC)
- The number of ports required (with room for expansion)
- The additional features needed
- Whether to use wired or wireless connection
- If audio capability is required as well as MIDI
- Will the unit be rack-mounted or not
Developers are creating an increasing number of apps for tablets and mobile devices, and interfaces are available to transmit data to the mobile device or use it as a trigger for instruments. These tend to use the standard dock connector for the tablet and, hence, will be dock and operating system-specific (i.e. Apple or Android).
MIDI interfaces, in common with many other items of electronic hardware, are generally built with few moving parts and, unless seriously abused by previous owners, will tend to be very reliable. The core electronics are unlikely to fail unless the unit is grossly mistreated. MIDI interfaces are built to be either freestanding or rack-mounted, and depending on type, their casework will either show general wear and tear or marking from insertion and removal to and from rack spaces. In either case, any damage is likely to be cosmetic and will have no effect on the operation of the unit. Damage can be caused to external hardware, such as switches, volume controls, plugs and sockets, or dust and dirt can gather in the sockets. Damage to these items is usually remedied by replacement, and contamination in the sockets can be removed with switch cleaning fluids or compressed air.
Finding a MIDI Interface on eBay
From the eBay homepage, select Browse by Category, and expand the category window to Show All Categories. Select Musical Instruments, and from the options in the left-hand pane, select Pro Audio Equipment. Again from the left-hand pane, select Audio/MIDI Interfaces, and from the Type selections, choose MIDI Interface. This should give a list of MIDI-only devices. Audio interfaces with MIDI capability are likely to be found by selecting USB Audio Interface from the same panel. Alternatively, a search for a specific brand or keyword can be made from the search panel at the top of any eBay page.
MIDI interfaces are usually robust devices, with few, if any, moving parts, and can generally be purchased with confidence, even when previously used. Musicians and producers should assess their current requirements with regard to the type of music production, whether exclusively electronic or a mix of acoustic and electronic work, and choose either a combined audio/MIDI interface, or a purely electronic MIDI-only interface, as appropriate, with further regard to the more specific buying points above.