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1.4.7. Routing and Multiplexing

Routing audio transmits a signal from one place to another — between applications, between parts of applications, or between devices. On Linux systems, the JACK Audio Connection Kit is used for audio routing. JACK-aware applications (and PulseAudio ones, if so configured) provide inputs and outputs to the JACK server, depending on their configuration. The QjackCtl application can adjust the default connections. You can easily reroute the output of a program like FluidSynth so that it can be recorded by Ardour, for example, by using QjackCtl.
Routing and multiplexing
Illustration of routing and multiplexing in the Connections window of the QjackCtl interface.
  • Master bus inputs accept multiplexed audio from many sources.
  • Master bus outputs routed to system playback inputs.
Figure 1.6. Routing and multiplexing

Multiplexing allows you to connect multiple devices and applications to a single input or output. QjackCtl allows you to easily perform multiplexing. This may not seem important, but remember that only one connection is possible with a physical device like an audio interface. Before computers were used for music production, multiplexing required physical devices to split or combine the signals.