Appendix
208
Iridium Manual
Glossary
Aftertouch
The majority of contemporary keyboards are capable of
generating aftertouch messages. On this type of keyboard,
when you press harder on a key you are already holding
down, a MIDI Aftertouch message is generated. This fea-
ture makes sounds even more expressive (e.g. through
vibrato).
Aliasing
Aliasing is an audible side effect arising in digital systems
as soon as a signal contains harmonics higher than half the
sampling frequency.
Amount
The extent to which modulation influences a given para-
meter.
Amplifier
An amplifier is a component that influences the volume
level of a sound via a control signal. This control signal is
often generated by an envelope or an LFO.
Arpeggiator
An arpeggiator is a device that splits an incoming chord
into its individual notes and repeats them rhythmically.
Most arpeggiators feature different sequence modes to
cover a wide range of applications. Typical controls for an
arpeggiator are the octave range, the direction, the speed
and the clock, which means the repetition interval. Some
arpeggiators also feature preset or programmable rhythm
patterns.
Attack
An envelope parameter. ‘Attack’ is a term that describes
the ascent rate of an envelope from its starting point to the
point where it reaches its highest value. The Attack phase
is initiated immediately after a trigger signal is received –
i.e. after you play a note on the keyboard.
Clipping
Clipping is a sort of distortion that occurs when a signal
exceeds its maximum value. The curve of a clipped signal is
dependent of the system where the clipping takes place. In
the analog domain, clipping effectively limits the signal to
its maximum level. In the digital domain clipping is similar
to a numerical overflow and so the polarity of the signal’s
part above the maximum level is negated.
