Apple Logic Express 7 - Manual (Page 76)

76 Chapter 12 Synthesizer Basics
Undesirable analog synthesizer phenomena, such as the habit of going completely out
of tune, are not simulated by virtual analog synthesizers. You can, however, set the
voices of the ES1 to randomly detune, adding “life” to the synthesizer’s sound. Unlike its
analog counterparts, the ES1 is also; completely programmable (you can save sound
settings), can be completely automated (you can record and playback fader
movements), polyphonic (you can play up to 16 notes at the same time), multitimbral
(you can play different sounds at the same time—on different Audio Instrument
channels), and velocity sensitive.
These are important benefits, which overcome the limitations of old synthesizers. If you
find it more inspirational to avoid the use of these features, you can always switch
them off.
What Is Synthesis?
Before we start, synthesis in this context, is the (re)production of a sound which
emulates, or synthesizes the sound of another instrument, a voice, helicopter, car, dog
bark—in fact, any sound you can think of!
This synthetic reproduction of other sounds is what gives the synthesizer its name.
Needless to say, synthesizers can also produce many sounds which would never occur
in the “natural” world. This ability to generate sounds which cannot be created in any
other way is what makes the synthesizer a unique musical tool. Its impact on modern
music has been enormous, and will continue well into the future—although it is more
likely to live on in “virtual” form, rather than as hardware.
Subtractive Synthesis
Subtractive synthesis is synthesis using filters. All analog and virtual analog synthesizers
use subtractive synthesis to generate sound. In analog synthesizers, the audio signal of
each voice is generated by the oscillator. The oscillator generates an alternating current,
using a selection of waveforms which contain differing amounts of (more or fewer)
harmonics. The fundamental (or root) frequency of the signal primarily determines the
perceived pitch, its waveform is responsible for the basic sound color, and the
amplitude (level) determines the perceived volume.