MIDI concepts MIDI is an industry standard to connect musical instruments. It is based on transmitting the actions performed by a musician playing some instrument to another different instrument. Musical instruments enabled with MIDI interfaces typically have two DIN sockets labeled MIDI IN and MIDI OUT. Sometimes there is a third socket labeled MIDI THRU. To connect a MIDI instrument to another one, you need a MIDI cable attached to the MIDI OUT socket of the sending instrument, and to the MIDI IN of the receiving one. You can find more information and tutorials like this one all around the Net. There are also hardware MIDI interfaces for computers, providing MIDI IN and OUT ports, where you can attach MIDI cables to communicate the computer with external MIDI instruments. Without needing hardware interfaces, the computer can also use MIDI software. An example is VMPK, which provides MIDI IN and OUT ports. You can attach virtual MIDI cables to the VMPK`s ports, to connect the program to other programs or to the computer`s physical MIDI interface ports. More details about this coming later. You usually want to connect the MIDI output from VMPK to the input of some synthesizer which transforms MIDI into sound. Another common destination for the connection would be a MIDI monitor that translates MIDI events into readable text. This will help you to understand what kind of information is transmitted using the MIDI protocol. In Linux you can try KMidimon and in Windows MIDIOX. VMPK doesn`t produce any sound. You need a MIDI software synthesizer to hear the played notes. I recommend you to try QSynth, a graphical front-end to Fluidsynth. In Windows you can also use the Microsoft GS Wavetable Synth that comes with all Windows versions, or a better alternative like CoolSoft Virtual MIDI Synth. Of course, an external MIDI hardware ©