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MIDI Sequencing and Synchronization
 MIDI Sequencers
allow you to record MIDI data much in the same way you would record an audio tape. You are presented with
"transport" controls such as Stop, Play/Pause, Fast Forward, Rewind, and Record, as well as multiple MIDI
"tracks" in which to record data basically in the same way analog multi-track recorders work. The number of MIDI
tracks is dependent upon the sequencing  software package you use, but it generally averages around 64 tracks - with some
having a few as 16 (one per MIDI channel). Some software sequencing packages allow you to have an unlimited number of MIDI
tracks for recording!
In graphics-based MIDI sequencers, the MIDI data is represented in a linear fashion where note events occur along a
horizontal timeline and each note's pitch is represented vertically. You also have the ability to set song position
markers so you can instantly move to any point in your composition using auto-locate buttons within the sequencer's interface.
Editing is accomplished in much the same way you would edit text in a word processor. Cut, copy and paste functions make
building musical segments a breeze.
Most packages allow you to make physical changes to the MIDI data stream to create the kind of multi
effects you would normally associate with an audio signal processor, but without any of the signal decay that can occur
with audio tape and analog signals. Effects such as delay, chorusing, arpeggio, and harmony can be automatically added to a
MIDI track with incredible ease... provided the software allows for it. Multiple MIDI tracks can also be merged into a single
track or even time shifted in relation to other MIDI tracks. Most of the advanced MIDI sequencing packages available for
the PC will normally have some sort of software based control for the most common pro and semi-pro audio mixing consoles
that have automated mixdown functions or faders.
MACKIE makes a great line of mixing consoles that can be remotely
controlled from a PC or Macintosh. Some sequencers, like
Steinberg's Cubase SX,
can even take your MIDI input and convert it to notes on a staff - even if you know absolutely nothing about musical notation!
As I mentioned, MIDI recorded into a computer-based MIDI sequencer is generally displayed in a linear fashion on a
horizontal time line. Because music is time-intensive, a sequencer must receive input from a clock or timer (don’t worry,
its not something else to buy, it’s part of the software). These clocks send tiny timing references in the form of
electronic pulses to the sequencer for every real-time second. In MIDI lingo, this reference is measured in Pulses Per
Quarter-note or PPQ. If a clock only sends 1 PPQ, then the only notes you would be able to record would be quarter-notes,
half-notes and whole notes. The lowest acceptable PPQ is 96. Notice I said "acceptable"... not preferable.
Ideally you want a sequencer with the highest PPQ resolution available. If you have a sequencer that has a PPQ of
96, this doesn’t mean that you can play 96 notes in the space of a quarter-note, that many notes played in the space of a
quarter-note would sound like a continuous tone... this is simply the timing mechanism that is used to place anything from a
64th-note to a whole-note within the time line of your composition. A higher resolution does allow you to more accurately
offset the parameters of tools that allow you to alter the MIDI data in relation to time. "Quantizing" is a good
example. In beat quantinization you can make those sixteenth-notes that you didn’t play just right, lock to the beat given
by the sequencer’s metronome or "click track". Having the ability to offset quantinization forwards or backwards
along the timeline using fractions of a tempo or note gives MIDI composers the ability to create unique "grooves"
that can give a musical passage just the right flair.
Try not to use quantinization too much, however. It is the timing
irregularities we humans introduce to music that prevents it all from sounding like it was created by a machine. Nobody
has the kind of perfect timing a computer has - so, quantize sparingly.
To play back a sequence, most MIDI sequencers default to their internal clock. MIDI sequence playback follows the same
rules that scored music follows: Beats per Minute and the standard (and not so standard) time signatures (4/4, 2/4,
3/4, 7/8, etc.) If you have a secondary MIDI device that you record information into, such as a
drum machine, you
can make the MIDI sequencer sync to the MIDI clock output of the external device or vice versa. There will normally be a
selection in the sequencer’s menu (or
drum machine
or whatever) that allows you to set the MIDI CLOCK to internal or
external. Using this method, you can control the playback of externally recorded MIDI data from a single set of controls.
You must make sure, however, that there is only one MIDI CLOCK source for all recorded MIDI data. More than one point of
timing reference can create some very weird music. Not very pleasant, unless you are into that sort of thing, or you're using
hallucinogenic che micals. I should note, however, that you can bring two MIDI signals together. The required
device is called a
MIDI Merger
which takes to MIDI signals, syncs them together and sends them out on
a single MIDI cable.
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