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Synthesizers are devices that electronically synthesize sound. In our case we are
synthesizing music but it could just as easily be a dog barking or an explosion that is
triggered by our incoming MIDI data. There are several varieties of synthesizers based on
the technology they use to imitate musical instruments. The most common synthesizer today
is some form of sampling synthesizer. In my last article I talked about digital audio and
samples being measurements of sound pressure at a moment in time which are strung together
to make a graph of sound pressure over time so a digital signal processor can use these
measurements to reconstruct an audio waveform. This means digital audio is sound broken
down into numbers and then numbers used to reconstruct the original sound. Just like a
sequencer can change the MIDI data before sending to the synthesizer, the digital audio
numbers can be changed by digital audio editing software so that the sound you play back
is different than the sound that was recorded. Sampling synthesizers use that ability to
take a recording of a few notes from an instrument and figure out what the non-recorded
notes should sound like. Not only does a Sampling Synthesizer, commonly called a Sampler,
use numbers representing samples of sound pressure and string them together to make whole
sounds; it also takes small samples of whole sounds from musical instruments (or anything
else) and uses them to make up all the notes of those instruments. The mid priced sampling
type synthesizers don't have the ability to record samples, only to manipulate them and
play them back. These devices must get the samples from a CD-ROM, floppy or hard disk. The
least expensive sampling type synthesizers can not record samples and can not receive new
samples from the outside at all and must rely on whatever samples are permanently encoded
in their limited sample ROM. There are synthesizers even simpler than this that rely on
single cycle wave forms and put them together in formulas to try to imitate real
instrument sounds. The waves are organized in the form of a table and the table is
referred to when the synthesizer is told which formula to use to make a particular sound.
The are true Wave Table Synthesizers. The earliest sound cards trying to sound better than
FM synthesis used wave table synthesis and this quickly become a multimedia marketing buzz
word so when the better Sample Based Synthesizers came along they were forced to declare
themselves "Wave Table" synthesizers to avoid being thought inferior by the
synthetically-challenged general public. Today nearly all decent sounding sound cards or
synthesizers are actually based on sampling synthesis but if they are found in a product
for a personal computer they are probably referred to as Wave Table synthesizers. Some
manufacturers have tried to shrug off that name by simply calling them Wave Synthesizers.
Since ALL synthesizers generate sound waves they are certainly not lying.
MIDI synthesizers are simply synthesizers that play music in response to incoming MIDI
data and can also often save their present settings by sending them as MIDI data to a
sequencer for safe keeping. At our last stop the train unloads its cargo of MIDI messages
into the MIDI Synthesizer and musical notes are generated. In order to hear these sounds
you will have to hook up an amplifier and speakers to your MIDI synthesizer but remember
what I said about only following one type of signal at a time? The sound generated by your
MIDI Synthesizer is not MIDI data. It is audio data just like what comes out of your home
stereo system. Unlike what comes out of your home stereo system MIDI triggered,
synthesized music is not carefully controlled to avoid destroying your amplifier and
speakers so you should use caution when working with synthesizers to protect your
equipment and your hearing. A MIDI synthesizer is often found as part of your MIDI
controller keyboard and vice versa just as I said that a sequencer also sometimes found in
a keyboard/synthesizer so you should not assume that the three stations our MIDI train
used means you necessarily need three separate pieces of equipment.
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