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What It All Means


Article from Making Music, September 1986

CHAIN: Sequencers save space and memory by breaking everything into repeatable lumps. If your new song needs 12 choruses, you write the notes once, and tell the machine to play them a dozen times. You save yourself just under 11 choruses worth of memory. The arrangement of repeated verses, choruses, middle bits, etc and the instructions on how often to spit them out is called a chain.

EDITING: It would be a very basic sequencer these days that didn't offer some form of editing. You ought to be able to at least delete one unwanted bar from the whole song, and insert a new one, without recording the whole piece again. Better facilities let you edit individual notes, copy bars, or fast forward through a piece like a tape recorder running at high speed.

GATE TIME: Not to be confused with note duration. You have a bar of 4/4, and a riff with four notes in it. Each one falls precisely on the beat, so each one is a crotchet (a quarter note long — see PQN). But you want the first not to be short and punchy. If you reduced it to one of those 16th note jobs (a semi-quaver) then once it was finished, the next crotchet would come hard on its heels and be 3/16ths too early. Bad news. Instead, you keep all the notes as crotchets and alter the gate time. This is a measure of how long the synth connected to the sequencer actually makes a noise during the lifespan of that crotchet. A short gate time gives you a snappy note and the remaining 3/16ths is filled with comforting silence until the next note turns up.

INTERNAL CLOCK: The clock, as you might guess, is the bit of the heart of a sequencer which makes it run on time, on the beat, and on demand. But you wanted the sequencer to run linked with a drum machine it makes sense to have one clock directing both machines. In this case, the drum machine could supply an external clock, and there would be sockets at the rear to make the connection.

KEY VELOCITY: These sequencers will also record how hard you hit the keys so your dynamic effects — providing your keyboard has them — are preserved.

MULTICHANNEL RECORDING: For the moment, at least, it's not quite the same as multichannel recording on a tape deck. With tape you have, say, 16 separate tracks which can all be individually edited, eq-ed or mixed whenever you fancy. If you made a mono mixdown of those 16 you'd still have all the music there, but you'd no longer be able to treat any of it separately. Along comes Mr Clever-knob who gives you a device which now allows you to completely turn off a track within that mix, of give it the sound of another instrument. But what you can't do is change the actual notes played. That's the state of the majority of budget sequencers at the moment. There's only one track but it can store hundreds of notes and remember that they should be played by an instrument on MIDI channel 1, at the same time as other notes are played on MIDI channel 2, and this lot on MIDI channel 3, etc. Because each layer has its own MIDI assignment (1-16) you can turn off channel 14, or decide channel 5 should now have a brass sound instead of string one. But once that MIDI layer has been recorded and blended with all the others, you can't rewrite it.

MULTIFUNCTION KEYS: Many modern bits of gear have these, but sequencers seem to suffer the most. To save on buttons, each switch may have to do several jobs, and which one it's doing at any time depends on what other buttons you've pressed and in what order. Not a problem, but make sure you read the manual.

PQN (Pulses per Quarter Note): A measure of the speed of the clock, and the common rates are 24,48 and 96 PQN — in other words, every time the clock puts out say, 24 pulses, the machine will advance through the sequence (ie 'play') one quarter note — a crotchet. (Brief musical aside: in a bar of 4/4 a whole-note or semibreve would last for all of it, a minim would take up half the time, and a crotchet would be a quarter.) Obviously it's important to match clocks otherwise a drum machine working at 48 PQN would drive a 24 PQN sequencer twice as fast as it should. Most sequencers are switchable and anyway, recent machines now use a standardised MIDI clock instead which presents no matching problems.


REAL TIME: (See Resolution). This is where the sequencer acts as a tape recorder. You turn it on, you play, it records, remembering your notes and your timing.

RESOLUTION: A sequencer is an ear with a big flap over it, believe me, and there are two ways you can make it listen. You can manually lift the flap up, shove in one note, and let the flap close (see Step Time). Or you can attach a motor to the flap so it's automatically opening and closing precisely in time with the beat while you play away in the corner (Real Time). However, if the motor runs too slowly el flappo will occasionally be shut at the wrong moment and miss a note. This is what sequencer designers mean by resolution or quantisation, and if you're playing fast polyphonic stuff, you want that ear opening quickly enough to capture everything and record it. Resolution is often expressed in note values — 16th notes (opening 16 times in a measure) is a common standard, but on machines like the Yamaha QX1 you'll be blessed with 384 flaps per measure. The higher the resolution, the truer the recording will be to the expression you put into the piece. Imagine if you played (and wanted) a note that started slightly before the beat — the ear would open part way through it, not know anything had gone before, and simply record what it heard. On playback that note would therefore begin precisely on the beat, the earlier bit having been lopped off. Conversely, late notes will be pulled into line, again starting spot on the beat. If you're not the most technically proficient of players a smart choice of resolution (it's usually switchable) can do you a favour as it will tidy up your fingering.

STEP TIME: (See Resolution). There are two main advantages to unplugging that ear manually. With Step Time recording the sequencer itself will playback the material to a precise beat, or you can edit the timing at a later date. All you're entering for the moment is the pitch information, a note at a time, so you can build up complicated, fast pieces which you wouldn't be able to play physically. And it takes up far less memory space. Real Time uses up memory by continually opening the flap even when there's nothing to record. Step Time only does it when there's a note to remember.

TEMPORARY BUFFER: You'll find this buried deep in the spec and under a variety of names depending on the manufacturer. It's a parking space, somewhere you can put a sequence you're working on a while you do something else.

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Publisher: Making Music - Track Record Publishing Ltd, Nexus Media Ltd.

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Making Music - Sep 1986




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