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What is a Sound Generator?
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There are three ways to play
MIDI music with PC. They are using FM Sound Generator, using Software synthesizer,
and using External Sound Generator. Sound Generator is a device that receives
MIDI command and generates corresponding sound. MIDI command describes
sound to generate, sucu as "Play note C with piano tone and make it length
of 4th note", while actual sound is waves of air. Therefore MIDI command
has to be transformed to wave of sound. Sound Generators do this process
for you.
You can think of WAV file of Windows.
WAV file is recorded as wave of sound while MIDI is recorded as commands.
These differences result in file size. Command that says "Play note C with
piano tone and make it length of 4th note" needs saveral bytes while recording
piano sound for a few seconds many bytes. |
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Methods of Sound Generation
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Each Sound Generator has a
different method to generate sound from MIDI command. FM Sound Generator
is embeded in PC's Sound Card. FM Sound Generator takes a MIDI command,
then modulates simple wave (such as sign wave) and make the sound. Imagine
the following situation. You draw a line on paper randomly and you can
regenerate the line using some polynomials and parameters. It may be not
perfect, but it could be good job if you spend some time. The sampling
method that will be shown later generates better sound, but good point
of FM method is that you can easily modify original sound. In the case
of former example, you can change parameters and get different sound.
Software Synthesizer and External
Sound Generater have (PCM) sampling sound of music instruments. It receives
MIDI command and regenerates sound from sampling sound. Software synthesizer
uses PC's CPU when it converts MIDI command to actual sound wave while
External Sound Generator uses its own CPU when generate sound. (External
Sound Generator is connected to PC with MIDI cable.) Even if it is a borad
that is in PC, if the borad has its own processor and memory, it is equivalent
to an External Sound Generator. When software synthesizer is used, if CPU
power is not enough, the generated sound offten breaks. External Sound
Generator has many prepared tone and many fanctions, so it is the best
sound generator.
The method of Analogue synthesizer
is that it combines waves such as sign wave and square wave, and generates
required sound. In the case of former example, to reproduce random line,
some polynomials can be combined. It is hard work to reproduce the original
line. |
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Comparison of Sound Generators
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Sound Generator
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Price
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Quality
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FM Sound Generator
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free(embeded)
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Low
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Software Synthesizer
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cheap(less then $100)
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High
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External Sound Generator
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expencive(around $500)
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High
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Links to topic related site
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External Sound Generator
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YAMAHA MU family
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ROLAND SC-88 family
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