1.4) What are definitions for the following things? - aftertouch, envelope, FM, LFO, module, multitimbral, polyphony, pressure, sampler, sequencer, synthesizer, velocity
Description
This article is from the Electronic and Computer Music FAQ, by Craig Latta Craig.Latta@NetJam.ORG with numerous contributions by others.
1.4) What are definitions for the following things? - aftertouch, envelope, FM, LFO, module, multitimbral, polyphony, pressure, sampler, sequencer, synthesizer, velocity
"AFTERTOUCH" -- same as "pressure"
"ENVELOPE"
Date: Thu, 17 Jun 93 15:42:55 +0200
From: styri@balder.nta.no
A set of parameters to shape (envelope) the sound with
reference to key press and key release, or rather note
on and note off. Envelopes have a varying number of
parameters, and they may be used for different purposes
like volume or filter control.
There are many different implementations of envelopes,
but most of them will have the following 4 properties:
Attack, Decay, Sustain and Release.
At "note on" the control signal described by the
envelope will grow at a specified rate. This is the
`attack' and it's usually limited by a time frame.
At this instance the signal will `decay' at a
specified rate (it may, however, continue to grow
though we still call it decay). When the decay stops,
eg. specified by another time frame, the signal will
be `sustained' until "note off". At this instance the
control signal will decrease at a specified rate.
Haakon Styri styri@nta.no
"FM" -- frequency modulation
"LAYERING" -- see "MULTITIMBRAL"
"LFO" -- Low-Frequency Oscillator
"MIDI" -- Musical Instrument Digital Interface
An international standard which allows communication between electronic
music and lighting equipment from various manufacturers.
"MODULE"
"MULTITIMBRAL" -- capable of playing two or more timbres simultaneously
From: awkerr@zia.aoc.nrao.EDU (Alan Kerr) (edited by K. Eno)
Date: 5 Aug 92
It means that there are multiple *timbres* on the machine: more than one
different sound can play simultaneously. A machine that is mulitimbral
*usually* will let you play those different sounds on different MIDI
channels. "Layering" causes the synth to produce more than one sound when
you press a single key. A "keyboard split" (or just "split") allows you
to play one patch (a piano, perhaps) on one range of keys while you play
a different sound (the bass) on another part of the keyboard. A
"velocity split" allows you to play different patches at different
velocities. For example, you could have "mellow brass" at low velocities,
"brass" at medium velocities and "screaming brass" at high velocities
played on the same keys.
"POLYPHONY" -- number of simultaneously playable voices
From: crispen <crispen@EFFTOO.BOEING.COM>
Date: 4 Aug 92
- Polyphony and multi-timbrality. The "polyphony" of a
keyboard is the number of simultaneous notes that it can
play. However, the polyphony advertised by the manufacturer
is usually greater than the polyphony you'll actually get,
especially with multi-timbral keyboards.
Imagine that you have a 16-note polyphonic multi-timbral synth.
If you have a multi-timbral sound that has two "raw" voices that
sound simultaneously, you're down to 8 different notes that can
sound at the same time (16 notes of polyphony divided by two
voices). This is true even if the two voices are the same raw
voice, but doubled to give a thicker sound. If you have four
voices in the multi-timbral sound, you're down to four notes
that can sound at once.
The real question, then, is how many voices (on the average) this keyboard requires to make up a multi-voice sound that's
useful. This will vary from one to four or more. A sampler,
for example, may only require one voice to produce exactly the
sound you want, while some kinds of synthesizer will take three
or more voices before the sound is halfway decent.
When you exceed the polyphony limit (and the rule is that you
never have as much as you want) different keyboards handle the
overflow differently; most turn off the "oldest" voice first;
some allow you to set the way overflow is handled. Some quiet
down the voice that's been turned off very subtly; others are
noisy. Many newer keyboards have "dynamic voice allocation"
(DVA) which allows you to guarantee a certain number of notes
on each raw voice; when you exceed the polyphony limit, the
keyboard will steal from other voices with lower guarantee
numbers so that you get more notes, but each note sounds a
little thinner because not all the voices are sounding.
You *must* check this out hands-on. Play the multi-timbral
sounds in the store with as many fingers on the keys
as you will use in normal playing for those sounds. If you
like fat two-handed minor 11ths, you'll need a lot more
polyphony than players who only play one or two notes at a time.
"PRESSURE" -- keyboard feature for sensing continuous key pressure
Keyboards which are pressure-sensitive (or have "aftertouch", which
is the same thing) can detect the amount of pressure on a key AFTER
it has reached the end of its initial travel; this data can be used
to vary the loudness or other characteristic of the sound, and usually
sent as MIDI continuous controller messages as well.
MONO pressure, also called "channel" pressure, detects the key that's
pressed hardest; POLY pressure senses the individual amount for each
separate key.
"SAMPLER" -- a device for recording and playing back digitally
recorded sounds (I know, I know, the Mellotron)
"SEQUENCER" -- a musical event recorder
"SPLIT" -- see "MULTITIMBRAL"
"SYNTHESIZER" -- device for producing sound through analog or algorithmic means
As generally used, a musical instrument which produces a sound signal
by means of either analog electronics or real-time, algorithmic generation
of a digital waveform. A variety of techniques are used:
Additive synthesis
Subtractive synthesis
Ring Modulation synthesis
Frequency Modulation synthesis
Phase Distortion synthesis
(But is a pipe organ a synthesizer? How about "real" instruments"?)
"VELOCITY" -- keyboard feature for sensing how hard you initially play a note
Velocity-sensitive keyboards detect how hard you play. Usually they do
this by measuring how FAST a note is played -- that is, by measuring the
delay between the initial strike and the time the key reaches the end of
its travel.
The information is usually used to determine the loudness of the note,
but can also cause effects such as a faster attack or a shorter overall
envelope, depending on the internal architecture of the sound generator.
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