X

Appendix B Synthesizer Basics 491
Other synthesis methods
Other synthesis methods overview
There are many ways to create sounds, using dierent technologies and approaches to
synthesis. This section covers all the main methods, with reference to Logic Pro instruments
where applicable.
Many of the methods described incorporate at least some elements of the subtractive synthesis
design. See How subtractive synthesizers work. The most common modern approach is based on
samples of real instruments and sounds.
Sample-based synthesis
Sample-based synthesis, which is sometimes known as Pulse Code Modulation (PCM), or sampling
and synthesis (S&S) synthesis, is dierentiated from subtractive synthesis mainly by the use of
samples in place of oscillator waveforms.
The samples—digital recordings of existing sounds—are mapped across the keyboard. Typically,
each sample is mapped to a note in the center of a keyboard range that spans a few notes that
are unique to that sample. The reason for this limited range of notes is that samples tend to
sound much less like the source sound if played more than a few notes higher or lower than the
original pitch—due to the relationship between the pitch and playback speed of samples.
The pitch of each sample isn’t changed with a frequency control, unlike the oscillator waveform
of a synthesizer. Rather, a sample is played back at a faster or slower speed to alter its pitch,
which has a corresponding impact on the sample playback time. For example, a sample played
back at twice the speed requires half the time to play through.
EXS24 mkII is a sample player that can be used much like a sample-based synthesizer, due to the
subtractive synthesis features that it oers.
Popular instruments that use this synthesis approach include Korg’s M1, O1/W, and Triton; the
Roland JV/XP instruments; Yamaha’s Motif series; and many others.