Three decades ago, keyboards were wedded to tone generators in the same
enclosure, and digital audio recording were expensive and rare—but then
MIDI appeared. MIDI is a digital language by which synths, sequencers,
and controllers talk to one another. Among its early benefits was
separating the keyboard controller from sound generators so that a
single keyboard could control multiple, less expensive, and typically
rack-mounted tone modules. MIDI also offered a high-quality “multitrack”
recording experience to composers and working musicians who couldn’t
have afforded their own multitrack tape machines. Today you can easily
record 100 tracks of digital audio on a basic laptop, so MIDI may seem
irrelevant in the studio. Yet MIDI remains not only viable, but valuable, because it lets you exploit today’s studio in ways that digital audio still can’t.
MIDI basics. Digital audio is a representation of sound itself—the
numbers involved are eventually converted back into a voltage that can
drive an amp or powered speaker. MIDI data is a set of instructions
that in turn tell something that can make sound—like a hardware or soft
synth—what and how to play. The classic analogy is the old-fashioned
player piano: The paper piano roll isn’t a recording you can play back
in the absence of the piano itself; instead, the holes punched in it are
read by a mechanism that then tells the piano’s hammers what strings to
Another good analogy is word processing. When you type on a
QWERTY keyboard, it generates digital data representing letters,
spaces, punctuation marks, and so on. This data flows into your
computer, which can then translate the data into pixels on a monitor so
you can see what you’ve typed, cut and paste words, email it, and so
forth. A MIDI musical keyboard translates your playing into data that
flows out from a MIDI output, then travels over a serial connection
(more on this later) into a synth, tone module, or your computer. The
data doesn’t equal the music anymore than the data from your
QWERTY keyboard equals your native language, but in both cases, the
former issues marching orders to a system that then creates the latter.
Having a set of instructions that can be saved and edited
separately provides all kinds of benefits. Before discussing those,
let’s cover a few more MIDI basics.
The MIDI interface.
MIDI’s interface protocol
differed from the ones used at the time for printers and other
peripherals. It used a five-pin DIN connector (see Figure 1 at left) for
the MIDI output that transmitted data from your keyboard or computer,
and another DIN connector for the tone module or computer MIDI input
that received data. Early personal computers needed an external
interface box that had MIDI connectors and converted the MIDI data to
and from a standard computer interface protocol. (Atari’s ST series and
Yamaha’s CX5M were two exceptions; they had built-in MIDI connectors.)
Most modern MIDI keyboards interface with computers over
USB; its advantages include eliminating a separate interface and
higher-speed data transfer. For older synths, DIN-to-USB converter
cables can provide a computer interface.
MIDI channels and ports. MIDI sends data over any
of 16 channels, and tone modules or virtual instruments can “tune in” to
a specific channel. For example, suppose you assign three different
synthesizers to receive data over MIDI channels 1, 2, and 3. Changing
the transmission channel on your controller keyboard (or on a MIDI
track’s output in your DAW) chooses which synthesizer will play. For
layering, you can set synths to the same channel. If your synth
can split or layer, this works by the keyboard transmitting on different
MIDI channels to the sound engine.
Eventually 16 channels weren’t enough, so interfaces (and
even some keyboards) started sprouting multiple ports—a four-port
interface can send data over 64 (four times 16) different channels. One
DIN connector equals one port, but a single USB connection can handle
multiple ports simultaneously.
Another development, the multitimbral synth, plays back
different sounds that respond to different channels. This is ideal for
computer-based multitrack MIDI recording and playback because data
recorded on one channel can drive (for example) a bass sound, while
another channel plays back a piano sound, another triggers drums, and so
Today, external tone modules have been upstaged by software instruments (see Figure 2 at left), but these still take their orders from MIDI. Now let’s consider some advantages of MIDI over digital audio.
Songwriting. If you start a composition with MIDI
instruments, you can transpose pitch and alter tempo easily. Transposing
simply tells the target synth to trigger notes that are a certain
number of semitones higher or lower. For this reason, there are none of
the artifacts associated with audio-based time or pitch stretching. Once
you nail the right tempo and pitch for your arrangement, you can then
start recording audio parts such as vocals. You can set up a
multitimbral MIDI instrument template with different instruments on
different channels, so as to get going quickly if inspiration strikes.
You can also record “placeholder” parts to keep the creative flow going
and not concern yourself with recording the perfect part, because MIDI
allows for . . .
Deep editing. Digital audio allows for broad edits,
like changing levels or moving sections around, and editing tools such
as Melodyne are doing ever more fine-grained audio surgery. But MIDI is
more fine-grained still: You can edit every characteristic of every
performance gesture: dynamics, volume, timing, the length and pitch of
every note, pitch-bend, and even which sound is being played. MIDI data
can tell a piano sound what to play, or if you change your mind, a
Clavinet patch. With digital audio, changing the instrument that plays a
given part requires re-recording the track.
Different types of editing.
“Piano-roll” editing is
the most common way to edit, but you can also edit on a musical staff
view, a grid optimized for editing drum parts, a spreadsheet-like list
of every single MIDI event in a part, and in some cases, even guitar tab
(see Figure 3 above).
These process MIDI data (see Figure 4 at left).
They can set minimum and maximum velocity limits, constrain notes to a
particular scale, repeat data for echo effects, change the order of
notes in a phrase subtly or drastically, and much more. Not all DAWs
accommodate MIDI plug-ins, but most of the majors do.
Mix and synth automation. In addition to notes, the
MIDI spec includes dedicated, numbered controller data options that can
control panning, level, modulation, sustain, and even amount to extra
hands turning your synth’s knobs as you play. With a multitimbral
instrument, controller signals can alter the mix by changing instrument
levels on the fly.
These are the basics, but MIDI can do much more—as you’ll find out in part 2 next month.Craig Anderton is the former executive editor of our sister magazine
Electronic Musician, one of the original gurus of music technology how-to, and currently the "Chief Magic Officer" at Gibson Brands.