Digital Sound & Music: Concepts, Applications, & Science, Chapter 6, last updated 6/25/2013
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pressure at which he or she is holding down the keys. Figure 6.27 shows some controls on a
synthesizer to apply After Touch and other incoming MIDI data to four different synthesizer
parameters.
Figure 6.28 After Touch modulation controls on a synthesizer
6.2 Applications
Linking Controllers, Sequencers, and Synthesizers 6.2.1
In this section, we’ll look at how MIDI is handled in practice.
First, let's consider a very simple scenario where you’re generating electronic music in a
live performance. In this situation, you need only a MIDI controller and a synthesizer. The
controller collects the performance information from the musician and transmits that data to the
synthesizer. The synthesizer in turn generates a sound based on the incoming control data. This
all happens in real-time, the assumption being that there is no need to record the performance.
Now suppose you want also want to capture the musician’s performance. In this
situation, you have two options. The first option involves setting up a microphone and making an
audio recording of the sounds produced by the synthesizer during the performance. This option is
fine assuming you don’t ever need to change the performance, and you have the resources to deal
with the large file size of the digital audio recording.
The second option is simply to capture the MIDI performance data coming from the
controller. The advantage here is that the MIDI control messages constitute much less data than
the data that would be generated if a synthesizer were to transform the performance into digital
audio. Another advantage to storing in MIDI format is that you can go back later and easily
change the MIDI messages, which generally is a much easier process than digital audio
processing. If the musician played a wrong note, all you need to do is change the data byte
representing that note number, and when the stored MIDI control data is played back into the
synthesizer, the synthesizer generates the correct sound. In contrast, there’s no easy way to
change individual notes in a digital audio recording. Pitch correction plug-ins can be applied to
digital audio, but they potentially distort your sound, and sometimes can’t fix the error at all.
So let’s say you go with option two. For this, you need a MIDI sequencer between the
controller and the synthesizer. The sequencer captures the MIDI data from the controller and
sends it on to the synthesizer. This MIDI data is stored in the computer. Later, the sequencer can
recall the stored MIDI data and send it again to the synthesizer, thereby perfectly recreating the
original performance.
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