MIDI, music and computers

Your computer is playing the backing tracks: bass, percussion, horn and string sections, piano, organ, and the drum machine is playing in sync while you sing or solo on your instrument. At the end of the song, within a few seconds all of the settings of the keyboards are cued up for the next tune. You composed these songs and recorded the different instrument parts into the computer in your bedroom studio, recorded a demo tape with the computer accompaniment, and got a printout of the complete score. Each instrument's part is ready for the big studio recording session next week...

A dream? With the appropriate computer and musical gear and software programs, all this is made possible by a standard called MIDI.

What is MIDI?
The Musical Instrument Digital Interface is the standard method for transmitting control signals between electronic musical instruments (keyboards, synthesizers, signal processors and others), and between MIDI musical instruments and computers. Its function is very similar to that of a computer network.

MIDI was pioneered in the early 1980's by Sequential Circuits in the US and Roland in Japan, and now has almost complete acceptance in the industry, from $250 home keyboards to megabuck professional studio equipment.

The MIDI network carries 16 channels of control information that can be used to play notes on MIDI keyboards or sound modules, control "expression" parameters such as loudness, pitch bend and vibrato, adjust the settings of signal processors, and store the settings of MIDI devices on a computer or data storage device. The most common use for MIDI is to "play" a keyboard or sound module from a computer sequencer program or from another keyboard.

What MIDI is not:
MIDI is not a "product" that you can buy; it is a standard method of communication that is now a feature of most electronic musical instruments. MIDI has nothing to do with audio. No sound is carried on the MIDI cables, just control signals. MIDI is similar in concept to the punched paper roll in an old player piano; the roll carries the information of what keys to press down, and for how long, but no actual sound. The piano produces the sound based on the "commands" from the roll. MIDI works the same way by sending control signals to MIDI instruments, which then generate the sounds.

What do I need to get into MIDI and computers?
The basic requirements for using a computer with your music are:
1) a computer (the Macintosh is the most popular brand for music)
2) a MIDI interface for the computer ( $ 125 - $ 800 depending on the sophistication of the unit ­ an entry-level interface would be adequate for a hobbyist)
3) one or more MIDI keyboards and/or sound generating modules
4) computer software for sequencing, and optionally, software for editing and archiving instrument patch data, or for printing musical notation
5) a sound system of some kind for amplifying and/or recording the music (a home stereo would do fine for a starting set-up. As you advance, you can add a mixer for combining the sound from multiple keyboards or modules, and a multi-track tape recorder for recording your work)

Do I need MIDI to make music with my computer?
Not necessarily - there are some programs that let you learn about music or play simple music directly from your computer. The sound quality and the flexibility are limited, however, so most musicians and hobbyists move to a keyboard with MIDI capability quite quickly.

What is a sequencer?
A sequencer is computer software that records the MIDI control signals from a keyboard as you play it, and allows you to edit the parts that you have played, add additional parts to it, and than re-play the sequence back through your MIDI keyboard or sound generating module. This allows you to be your own band, by "recording" each instrumental part one at a time, and then having the computer play it back all together. The number of parts that you can play back at once is limited by the number of different sounds and notes that your keyboard and/or sound generating modules can play at once. In the sequencer software, you can correct mistaken notes, add parts that would be too difficult to play by hand, change tempo, and change the pitch of one or all the notes.

Some MIDI keyboards have sequencing capabilities built in. The attraction of computer sequencer software is that you have a graphical display on the computer screen which makes it much easier to edit and assemble sequences, your sequences are generally not limited in their length (as some of the built-in sequencers can be), and you have unlimited storage of sequences onto your computer's hard drive or floppy disks.

Some computer software generates music from general guidelines that you give it. Band-in-a-Box is a popular one, because you don't have to record into it each instrumental part; you tell the software what style, what key and what tempo the song is, and input the chord changes. It generates the backing tracks for you. This is excellent for practicing improvisation or singing. Other software uses mathematical algorithms to generate music from scratch. These can be used in experimental music, or as a source of fresh ideas to stimulate you own creative processes.

What is the difference between a keyboard, a module, a sampler and a synthesizer?
A MIDI keyboard is a piano-style musical keyboard with MIDI circuitry that allows it to send MIDI signals to other MIDI devices. It usually has sound-generating circuitry inside it, which can be sample playback, synthesizer, or a combination of these two methods (although there are a few models which are built to be MIDI keyboard controllers only, and don't have their own sound circuitry). If it has sound circuitry, it will also respond to MIDI commands from other keyboards or sequencers.

A sound generating module is the sound circuitry alone, without any piano keyboard. These are usually in a small case, and they are an ideal way to add more sounds to your electronic orchestra. Once you have a MIDI keyboard and/or a computer sequencer, you don't need to buy additional piano keyboards, you can just buy the sound module and control it via MIDI. Yamaha, Korg, Roland, E-mu, Peavey, Kurzweil, Ensoniq and Kawai all make good keyboards and sound modules. Check to see that the unit you are considering is fully MIDI capable and multi-timbral (able to play many different sounds independently via MIDI control).

A sampler is a sound module or keyboard which has digitally recorded "real" sounds in its memory banks which it plays back when you play on its keys or send it MIDI signals. Most samplers on the market are sample-playback units only - you can play the samples provided by the manufacturer, but you can't record your own. A true sampler has a microphone input that lets you record your own sounds and edit them, store them in memory or on floppy disk, then play them back from the keyboard or via MIDI.
Samplers and sample playback units are capable of very realistic imitations of "real" instruments, and most MIDI setups will include at least one. Popular sample playback units are the E-mu Proteus series, the Roland Sound Canvas, the Yamaha MU series and the Korg M1/M3 series. Roland, Yamaha, Akai and E-mu make true samplers.

Drum machines are specialized sample playback units with a variety of drum sounds in memory. They have memory for patterns of rhythms that can be chained together to make complete songs, and they can use MIDI timing signals to play in synchronization with the rest of your system or can be controlled directly from a computer sequencer through MIDI . Roland, Yamaha, Korg and Alesis make good drum machines.

Some computers have a limited sampling ability (see What is Digital Audio, below), and some samplers are available as add-in cards for the computer. In most studio and performance music situations, an external sampler or sample playback unit would be preferable.

Apple has licensed some of Roland's General MIDI sounds and included them with recent Macintoshes. This will give programs the ability to play back MIDI sequences and generate the sounds in software, rather than having to use an external sound generating module. Not all sequencer software is capable of using this facility yet, but more will take advantage of QuickTime Musical Instruments as they are updated.

A synthesizer creates sound by combining or mixing electronic waveforms and manipulating them with a variety of controls. While synthesis can be used to imitate "real" instruments, it can also be used to create entirely new sounds. Some synthesizers take a hybrid approach by starting with sampled instrument data as the waveforms, and manipulating them further.

What if I play guitar (or sax, or violin)?
There are MIDI controllers available for many different types of instruments, so that if you have skills at playing an instrument, you can use them to control a MIDI setup. MIDI guitars are the most common, which are guitars with special pickups that sense the pitch of each string and send a MIDI signal to keyboards and computers. MIDI violins, trumpets, saxes, drum pads and accordions are also available, as well as converters that will track the pitch of a microphone signal, such as from a voice or a flute. Each of these controllers has its own trade-offs in capability and difficulty of playing. Practically speaking, a piano-type keyboard is still the simplest way to work with a computer/MIDI system, and even if a MIDI guitar is in your future, count on getting a MIDI keyboard as well.
Remember that a MIDIed acoustic instrument or controller is a one-way proposition. You can use your MIDI violin to input MIDI signals to the sequencer or sound modules, but it doesn't work in the other direction; the sequencer can't play the violin (or sax or guitar) for you. The closest you'll get is playing back a sample or a syntesized version of the sound. Don't expect keyboards give an perfect simulation of a real instrument. It takes a lot of skill to play a synthesized or sampled sound convincingly, and real instruments have significant variations in the tone and articulation of each note, which is beyond the ability of keyboard technology to reproduce.

What other things is MIDI good for?
MIDI can be used to control other events that occur in time, not just musical notes. Many signal processors and effects devices have MIDI capability, which allows their presets to be changed from a sequencer command. This is particularly good for performance, where the sequencer can automatically set all the instruments and devices to the proper settings before each song. MIDI commands can also be used to control certain parameters of some devices as they are being played. This can allow greater degrees of expression in performance or in recorded sequences.
MIDI is often used as a way to transmit the settings, or patches, of keyboards and sound modules to a computer, for storage, and for editing with patch editor software, which can make programming new sounds much easier. Digitally sampled sound files can also be transmitted over MIDI. MIDI can also be used to control stage lighting rigs, for light shows that are co-ordinated with the music, to co-ordinate sound tracks with multimedia or video presentations, and to control mixer settings in the studio for automated mix-downs in the studio.

What is Digital Audio?
A new development in the computer music industry is digital audio, which is an extension of digital sampling technology. Because sampled sound is digital data, just like the information on an audio CD, it can be stored on a computer's hard drive. This means that a computer with the appropriate hardware can store sound and manipulate it. To do this, the computer needs to have an Analog to Digital Converter (ADC) to sample the audio and turn it into digital data, and a Digital to Analog Converter (DAC) circuit to convert the data back into sound for playback. This technology is essentially the same as in CD players and DAT tape machines, but must be designed specially for the computer and have specific software to control it. Digital audio and MIDI are separate things, although they can be used in conjunction with each other.

Most Macintosh computers have microphone inputs and ADC circuits for sampling built-in, and all Macs have DAC circuits for playback. PC's can get these functions through add-in interface cards. The important thing to remember about these sampling features is that they are usually 8-bit ADC/DAC's, which means that their sound quality is limited. Quality sound reproduction requires 16-bit sampling at a frequency of 44.1 KHz (the CD standard). While the built-in capabilities of older Macs and the inexpensive sound cards for the PC are adequate for computer games and some multi-media presentation work, they are not high enough quality for musical recording or performance.

The exception to this rule are the PowerMacintosh and Macintosh Quadra AV-series machines. These machines are equipped with 16-bit sound in and out, and can be used for high quality digital recording. Deck II software from OSC works with the built-in sound circuitry of PowerMacintosh and Quadra AV machines to provide between four and twelve tracks of digital recording within the Mac.

Third party 16-bit add-in cards can deliver CD-quality sound, and the recording and playback features are determined by the sophistication of the card and software. There are a number of excellent systems on the market, which can go as far as replacing traditional multi-track tape recorders in a studio entirely. The best systems offer an unheard-of degree of control for editing and manipulating the sound. 16-bit systems are relatively expensive, ($ 1,000 to $ 10,000 not including the computer) and require a high performance computer with expansion slots and lots of hard drive space; a stereo audio signal sampled at CD quality takes about 6 Mb of storage per minute of playing time, so the hard drive storage requirements can be huge.

Where do I go for more information?
A good place to start is on the magazine rack. Keyboard, Electronic Musician, and Home & Studio Recording are three excellent magazines with enough basic information for the beginner and enough techie stuff for the expert. Any book on MIDI or recording written by Craig Anderton or Tom Darter is worth picking up, as is the Music and Sound Bible by Chris Yavelow.
In Victoria, Tempo Trend on Burnside Rd., Ward Music on Fort St. and Long & McQuade on Quadra St. all have good electronic keyboard departments. Ask your computer dealer if they have staff who are experienced with MIDI. Join a computer user group and start asking questions.