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Synthesizers
Patches (instruments)
The sounds are what people buy the synths for.
Used to be patch cords were used for the early analog synths to get
a particular sound, so the term, patch, has apparently
stuck for a particular voice or instrument.
These patches can be programmed based on the oscillator(s) sending out the tone.
Or samples, such as in 'wavetable' synths, can be included in
sample ROM (or RAM, if you make your own) to sound like particular
instruments.
Since each manufacturer's synth is so different, one program or
modifications to the basic tone, even the various built-in samples,
may be triggered one way for one piece of equipment, and entirely
another way for a different synth.
And there are numerous sites on 'the web' dedicated to particular
synthesizers and manufacturers of same.
The GM standard is supposed to run across all manufacturer's line of
synthesizers.
Instruments specified by number should be available, more or less,
on any GM compatible synth that's been made.
It sets out 128 voices or instruments, broken down into 16 general groups
of eight instruments each, with the drum set being a special case.
While this is covered in some detail
elsewhere, things
may not always sound the same from manufacturer to manufacturer, since
their method of generating sampled instruments will not be the same.
And FM synthesis, at least that found on OPL-3 soundcards, is almost a curse
to MIDI, the sounds are often so bad.
Even so, some instruments, in a particular octave, matched well with
certain other instruments,
and assisted by software drivers, can produce some pleasing
FM sounds (the Pachelbel Canon in D is often a good FM soundcard demo).
For sampled 'wavetable' sounds, some sort of guitar might have appealed to
one manufacturer, another rather different sort to another, both assigned
to the same guitar # in the GM 128.
So even for GM compatibility, even for sampled instruments,
the song could take on a very unexpected sort
of tone from one synth to the next.
The MIDI is still just a player piano roll, and not even all player pianos
sound alike.
As mentioned, the GM standard sets out 16 groups of instruments;
regardless of whether the instruments are generated from FM, or samples,
or whatever else.
Eight different instruments per category:
- Piano, incl. harpsichord and clavinet
- Organ, incl. harmonica ('mouth organ') and accordian
- Guitar, incl. acoustic ('jazz'), overdrive and distortion
- Ethnic, from bagpipe to fiddle
- Bass, incl. slap and synth basses
- Brass, from trombone to tuba to synth brass sounds
- Woodwinds
- Reeds, oboe to saxophone
- Strings, violin to harp, and with timpani thrown in
- Ensemble, full strings sections, full choir, orchestra hit
- Synth leads, various incl. the square and saw waves
- Synth pads, which often are among the best sounds in FM
- Synth sound effects
- Sound effects, from the sound of applause to birds chirping
- Percussion, wood blocks, bells, and so on
- Chromatic percussion, from xylophone to vibraphone to church bell
These will be set by sending a program change command to the synth.
And the above list is not necessarily in numeric order, but does show
the 16 categories for GM.
An additional command, a control change using controller #0, can
be sent to those synths which expand on this 128 using bank selection,
or whatever.
Your sequencer should handle these details, and rather just present
you with the list of instruments you can use.
The Roland GS, for example, has 354 instruments, with various
additions to the eight each in the above categories, and also
throwing in some patches from a couple of older synths produced by
Roland, the MT-32 and CM-32P (though not all GS synths include patches
from these two, the SCD-15 and strict compatibles will).
The 'super-GS' SC-88 Pro from Roland increases that number quite a bit more,
as do the XG synths from Yamaha.
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