MIDI Hardware: Interface -- A MIDI interface provides a link between a Mac serial port and MIDI device(s). For example, Altech Systems offers an inexpensive, light-duty, self-powered interface which has three MIDI-outs, one MIDI-in, one serial in, one serial out with a MIDI bypass switch for a direct serial-in to serial-out connection (useful if you use an external modem and don't wish to spend your free time switching cables between MIDI and modem), and three LEDs to register serial and MIDI traffic. It draws power from the serial port - an improvement over older models which had bulky power supplies. It is possible that some interfaces that depend on the serial port for their power may not work with a PowerBook.
Then there are the AC powered mid-line interfaces like Studio-2 from Opcode. At the upper-end, you can buy Mac-MIDI interfaces with up to 16 MIDI ins and outs, SMPTE converters, internal MIDI processing and routing, and much more (MIDI Time Piece from MOTU, Studio-4 and -5 from Opcode, etc..) These industrial-strength interfaces use special protocols and do not work with ordinary MIDI applications - unless you use OMS or something equivalent.
Interface products are also available from other manufacturers such as MacNexus and MIDIMAN. Apple too, sells an interface with one MIDI-in and one MIDI-out. However, if you plan to expand your MIDI system in the future, get an interface with more than one MIDI-out port. Make sure the package you buy includes at least two MIDI cables (DIN 5 pin 180 degree male/male) and a null serial cable. Prices for the "light duty" models run around $90 list, $60 street.
Macs -- Some PowerBooks (140, 145, 160, 165c, 170, and 180) with their disposition for imposing serial-port blackouts can be frustrating MIDI platforms. However, a combination of using the PowerBooks in Don't Rest mode and keeping AppleTalk on may help keep MIDI-data loss to a minimum. However, on PowerBooks with only one serial port, like the PowerBook 100, AppleTalk interferes with the serial port and must be off for MIDI use. As mentioned earlier, MIDI Manager automatically disables the Rest mode.
Reportedly, the Duos 210 and 230 have no problems with MIDI. Tests have established that the PowerBook 100 is fine at MIDI speeds - just. However, the PowerBook 100 may fail with special high speed interfaces. The PowerBooks 140, 145, 160, 165c, 170, and 180 can do easy MIDI chores such as simple record and play-back, but falter when receiving large amounts of MIDI data. In one series of tests conducted on a PowerBook 140, a great quantity of input MIDI data was lost, not just long sysex dumps as Apple maintains (a sysex dump is a bulk, high-speed data dump from a MIDI device to the Mac.)
A Tech Note suggestion (TN 318 - PollProc) by Apple was augmented and implemented by Opcode in a new version of OMS, 1.2beta. Under 1.2beta, the problem of lost MIDI data on the offending PowerBooks 140, 145, 160, 165c, 170, 180 is solved, but incoming data loses its timestamping. However, not all commercial programs are OMS compliant, and the TN 318 fix works only for interfaces attached to the modem port. The printer port continues to be unreliable for input.
MIDI data can be lost on the PowerBooks because they suffer from periodic serial port blackouts, which can last as long as six milliseconds (blame this on the Power Manager). Theoretically, as many as 30 bytes of MIDI data can be transmitted from a device to the Mac during a six millisecond span. During a blackout, only three bytes can be stored by the serial port's buffer. In the worst case, it is possible that as much as 90% of the data transmitted during a serial blackout could be lost. Regrettably, MIDI Manager predates PowerBooks and is blissfully unaware of PollProc calls. Further, some who have tried the solution in TN 318 suggest it is incomplete and does not quite work as advertised. Were it not for OMS, the functionality of the PowerBooks 140, 145, 160, 165c, 170, and 180 as complete MIDI platforms would be impaired.
The PowerBooks with their slim form and light weight are otherwise ideally suited for real-time MIDI performances. It is puzzling that Apple allowed some technically minor, but functionally disastrous problems to fester on most PowerBooks. Among the portables, the buying recommendation for a MIDI platform is a Duo. If you can find one, a PowerBook 100 can be a bargain platform for simple MIDI work.
Controllers -- Most people associate MIDI controllers with keyboards, but they can be anything you pluck, strike, or change in some way. For sanity's sake we'll limit discussion to keyboards and sound modules (keyboard-less synths).
Samplers and Synthesizers -- Thus far, we have used the terms "synth" and "synthesizer" for illustrating various MIDI functions. But samplers have equal status with synthesizers - you can get keyboard forms of both.
Samplers contain (in ROM or RAM) a literal hi-fi recording of a real instrument. The E-Mu Proteus is the most famous sample-playback module, while the Fairlight CMS and the E-Mu Emulator are probably the best-known sampling keyboard systems. Samplers can also be rack-mounted studio effects devices, and there are probably 40 or 50 samplers at all prices between obsolete models on the used market and new models. Some do not use MIDI.
A synthesizer builds sounds from simple waveforms blended together, from a combination of samples and waves, or by intermodulating a handful of waveforms (FM synthesis, the "DX7 sound," and also used to death in a poor-sounding 4-wave chip on most PC "Sound Whacker" add-in cards).
Do not pinch pennies when buying a keyboard. There is a marked difference between the inferior and the better ones. But you don't need a fancy keyboard if you are not a trained musician - just one you are comfortable with. After all, sequencers offer "step mode," which allows them to be slowed way, way down so even a talentless hack can play amazing MIDI shred arpeggios. If you're new to all this, a used Kawai K1 is a good inexpensive keyboard to look for. (On the other hand a $1,500 synth is in some sense, as good as it gets.) If you're planning only to edit and play back and you are not a trained musician, any keyboard is functional (yes, even a CZ101 will do just fine, thank you.)
You'll want a sound module with "good" sounds (preferably General MIDI compatible). The Roland Sound Canvas is a good value for beginners. Yamaha, Roland, and Korg all compete in the value-priced sound module market.
Here are features you can use to evaluate synths and define your musical priorities:
Number of octaves: A five octave range (that is 61 keys) is sufficient for most casual users. A 76-note keyboard would be considered a minimum for controlling several modules during a live performance. For playing Debussy, you'll probably want 88. Some keyboards have the ability to shift (or transpose) which adds two (or more) octaves.
Key size/feel: Does it matter if the keys are slightly smaller than usual? Do they have the feel of a piano key? If you are used to playing the piano, these considerations make a difference. Most of the better synths have full-size keys. Some offer weighted keys.
Polyphony: Polyphonic synths can play more than one note simultaneously. Thus, when a chord is played on a polyphonic keyboard, all notes of the chord sound. If the synth is monophonic and a chord is played on it, only one note of the chord will sound. However, a 32-voice polyphonic synth does not necessarily imply that 32 notes can be played simultaneously since each note itself could be made up of more than one voice. (Technically, the correct usage should be waveform instead of voice.) Polyphony is a must for serious MIDI-dabblers. Since almost all modern synths are polyphonic, this may not be a deciding factor.
Multitimbral: A multitimbral synth can play more than one musical instrument sound (patch) simultaneously. A synth could be polyphonic and able to play many notes simultaneously. However, if it is not multitimbral, all notes will play by only one instrument, for example, entirely as Hammond organ. A multitimbral synth could give you a string bass on the bottom, a piano in the middle, and saxes on top. This is another must feature if you want lots of instruments at once, and don't want an apartment full of synthesizers.
Velocity Sensitive: How loud a particular note is supposed to sound is embedded in MIDI messages as velocity. Velocity numbers range from 0 (0 is note-off; 1 is the quietest) to 127 (loudest). Most synths have velocity sensitive keys - when a key is struck, not only is the note and duration transmitted, but also how hard the key was hit (actually, how quickly the key moved).
After-touch: A type of touch sensitivity where the synth senses how hard the key is pressed down after it has reached (and is resting on) the keybed. After-touch is useful for assigning special effects and is commonly used for "expression" - to swell a sound, like a conventional instrument.
Sound quality: Most people consider this the most important factor (and rightly so). After all, you have to listen to the sound produced by your synthesizer. If the sound quality is inferior, even playing Bach will not help the music sound pleasant. Some synth models have digitally sampled sounds of various instrument stored in ROMs. Not surprisingly, these samplers sound pleasing when used for conventional orchestral, rock, or jazz music.
Miscellaneous: How many (and which) instruments can the synth emulate? Does it have a ROM slot that would allow expanding the internal instrument list by adding ROM cards? How easily are these cards available? Does the synth have waveform editing features? Can it do special effects? (You'll be surprised what just a simple reverb or delay can do for synth-sounds). Does it have adequate RAM (or a RAM slot) to save waveforms of customized instruments you create? Besides the standard MIDI-in and MIDI-out, a MIDI-thru port might provide more flexibility in configuring various devices on a complex MIDI network. General MIDI capability is essential if you plan to purchase and play libraries of commercially-produced MIDI music files.
Casio, E-Mu, Ensoniq, Peavey, Kawai, Korg, Kurzweil, Roland, and Yamaha are a few of the dozen-odd companies currently marketing electronic synthesizers (Casio has exited the musical/professional synth market and only sells inexpensive home units). Before starting your synth hunt, get a copy of the FAQ maintained by Craig Latta for rec.music.makers.synth on Usenet (FTP-able from <xcf.berkeley.edu>). It has useful pointers on buying your first synth. A used synth price list (available by FTP from <sprite.berkeley.edu>) posted every few weeks on the discussion group can help you shop around. This group is a good place to pick up used equipment, and solicit hardware and software recommendations. Keyboard and Electronic Musician are two magazines which are good newsstand resources.
Coda -- MIDI is often given superlative billings about how it can enhance your musical abilities and transform you overnight into a great musician. MIDI does give you precise control over the way your music sounds, but the greatness depends on you. Why, MIDI wasn't around until 10 years ago, and we did have a wee bit of good music before then.
You might not have enough money to buy all elements of a dream Mac-MIDI system (or for that matter, even a dream Mac system!). However, you can put together a simple MIDI studio comprising of a Mac and a synth easily and inexpensively. Aim for an open system that can grow easily by accepting new MIDI devices.
With the advent of 16-bit DSP chips in Apple future-ware, one area bound to see a proliferation of new products is the integration of digital sound and MIDI. Opcode's Studio Vision with Audiomedia (list $1,995) is one such Audio/MIDI package as is Digidesign's Pro Tools (list $5,995). Both are MIDI/Direct-to-Disk recording environments, or "tapeless studios." Expect to see digital audio/MIDI cards incorporating Ensoniq and Kurzweil chipsets in the future. In fact, a number of the programs mentioned earlier already offer SMPTE timecode synchronization of MIDI tracks onto video and digital audio master tapes.
MIDI has opened doors to exotic possibilities, and new MIDI instruments, software, and all kinds of MIDI accessories (like MIDI lighting controllers for stage lights, gloves with embedded MIDI controllers, etc.) are continually being introduced. There is MIDI software that introduces variations into the data you feed it; MIDI controller wands you wave, innumerable MIDI drumpads and variations thereon; MIDI marimbas; MIDI guitars; basses, violins, and wind-instrument controllers; MIDI floorpads you step on; MIDI sensors that pick up light, sound, or movement; you can do it all. For those of you into creative self-flagellation, at least one guy designed a MIDI drumset into a jumpsuit.
You could even create a MIDI file by transforming the last ten years' Dow Jones daily closing average as the lead voice and that day's high temperature in Manhattan as the backup. Just don't play it back for us.