Purchase the right interface to meet your needs. If your music setup includes only MIDI instrumentation, purchase a simple MIDI interface. If it includes traditional instruments in addition to digital instruments, consider purchasing a complete audio interface with MIDI ports, RCA ports, XLR ports and 1/4-inch instrument ports. If your computer is FireWire-enabled, consider purchasing a FireWire interface for faster transfers, otherwise purchase an interface with USB connectivity.
Insert the interface CD-ROM into your computer's disc drive and double-click the installer. Each audio interface includes an installer CD containing the necessary drivers that allow your computer to recognize and communicate with the device. You must install the drivers before you can connect.
Plug your interface into your computer using a free FireWire or USB port, depending on the type of interface that you selected.
Connect your MIDI device to your interface using a MIDI cable, available at electronics retailers and music supply stores. Insert one end of the cable into the "Input" or "MIDI In" port on the interface and insert the opposite end into the "Output" or "MIDI Out" port on the back of the instrument.
Turn on the interface if it contains a power supply. Some interfaces, particularly those containing built-in mixers, require electricity from a wall socket and contain an On/Off switch.
Open a program on your computer that interprets MIDI notation. This includes many digital audio workstations like Pro-Tools, GarageBand and Reason. To play your MIDI instrument, select a MIDI track on your computer screen (usually appearing in the left column of the audio software browser, indicated by names such as "MIDI Track 1," "Instrument Track 1" or "Software Track 1," turn on the instrument and begin playing.