In midi, what you record is not the actual sound, but, instead, the note number, velocity, and duration, along with some other more complicated information, like aftertouch, pitch bend, and effects. So when you playback a recording, it's like the old "player pianos" in that the music is "played", literally, as if you had several instruments all playing notes, the musical sound that you hear being "generated" by each note that plays.
The better the synthesiser, the better the overall sound of the "band". The FM sythesis in the Yahama OPL-3 synthesiser, available in many Sound Blaster (C) and compatible sound cards is a low end synth. The AWE32 Sound Blaster (C) is a WAV table synth that is an above average sounding synth. It works by playing a "sample" of the original instrument, giving it a more "realistic" sound. There are much better one's that expand on the sampling method, allowing for a more precise sample of the original instrument, along with models of the instrument that allow the sound to be altered, on the fly, to simulate the real instrument more accurately. These synths sound so realistic, that only an expert MIGHT be able to tell the difference.
My current equipment list includes an Ovation Adamas guitar, Cakewalk Pro Audio 7.01, AWE32 sound card, Yahama KX-76 controller keyboard, Alesis DM5 18 bit drum synth, Korg M3R synth, Alesis Micro Verb stereo sound effects processor, Yahama MU-90 XG synth, a 2 in, 4 out, parallel port Midiman Portman 2X4 midi interface, and a Mark of the Unicorn 7 ch stereo midi mixer. I usually have the DM5 on drums, and the MU-90 playing the rest. The total sound is impressive, even for this meager rig.
I would like to mention the MU-90. This is the best sounding synth I have ever heard, to date. It has great guitars, strings, horns, keyboards, and drums. It was a little pricy, around $700, but if you can afford it, you won't be dissapointed. It has hundreds of patches (sounds) and 6, 24 bit effects loops. It is also a 64 note polyphonic, 32 channel synth.You can see it at Yahama's site at http://www.yahama.com.
An added benefit of Cakewalk Pro Audio, is the ability to record 44.1 Khz audio (up to 8 tracks with an AWE32 card) along with the midi. This allows you to record harmony voice parts that come in during the song, to really knock their socks off. By the way, I play my midi along with a live guitar, or two, live harmonica, and live voice, along with live keyboard sometimes.
If you take the lazy approach, it does sound like a music box, and not much better. I prefer to record my midi compositions by playing the keyboard in real-time, half speed. I'm not a keyboard player, at least yet, and slowing down the metronome makes it easier for me to input the notes. But you can accent certain notes and get a lot of dynamics into the recording, not just a perfectly syncopated sequence of single velocity notes (music box). Plus you can make several "takes" and then cut and splice to make a better sounding "take". An average, good quality midi file of about 5 minutes length, is around 100KB. The equivalent length CD audio file would be several MB!
Here's an MP3 of me and my midi rig. I used Cakewalk and the MU90 for all the instuments and the DM5 for drums. There are a few sour notes but all in all it's not terrible.
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