RE: Midi (Akai-MPC25000XL)
I don't have an MPC, Fillup, but I want to help. DAW means digital-audio workstation. It's a computer that has capability to record and playback audio and MIDI, and it usually implies that the computer is dedicated for that purpose. It doesn't have to be, but it's better that way for serious composition with a minimum of hassle.
MIDI is just the digital information part; a bunch of numbers that don't produce sound on their own. But MIDI causes a sound module to act in a prescribed manner. Consider it as a conductor, dictating what the individual players are to perform. The conductor will give out the exact same instructions each time for a particular piece. But the sound that comes from each individual player will differ in interpretation from "instrument" to "instrument", and player to player.
So, MIDI goes in two directions: from the conductor to the player, and back again. Either the computer or the external (even internal) synth can take on either "role". One transmits; the other receives. Sometimes both. To keep everybody straight, MIDI has channels. An Omni setting sends all the MIDI information down all 16 channels. If you're only transmitting on channel 1 (usually a default transmit channel), you want the "player" to hear only what comes in on channel 1 (the receive channel side of things). So, you set up each instrument to it's own channel, and let the "conductor" talk to it over this channel alone.
Many times, MIDI convention puts drums on channel 10. Drums don't have to be there, but they often are. Something to keep in mind. Now, when you have all of this information exchanging hands, you still need a place to hear it. That's where the audio hookup comes in. The MIDI information can get recorded and sent back & forth, but it's still just a bunch of numbers. Translating that into an audio format that you can hear (and the computer can record & playback) is a separate step entirely. But you need both to complete what you're out to accomplish.