Audio Connections

The stereo inputs and outputs of both G4s are connected the the machine room mixer, which is also connected to a stereo audio monitor in the machine room. (If necessary, a mono monitor is acceptable.) The audio quality of the monitor is of no great importance.

The manifold audio signals

There are signals coming from microphones in the auditorium; there are signals from the computers described in the simplistic box "computer music stuff" on the Machine room setup page. A mixdown of these signals arrives at the "recording mixer" box pictured in the above illustration. This mixer supplies whatever mixdown of these signals is needed by the recording engineers to make a high-quality recording of the unique concert event.

It would be a good idea to solicit the recording engineers' generosity in providing a stereo or mono feed of of this mixdown to outputs connected to the "mixdown" inputs of the machine room mixer. The result we call, in our scientific naîveté, the input from the concert.

Input from the Concert

During the concert, a two-track mixdown from the recording mixer is sent to the machine room mixer, which reduces the signal to mono and sends it to the G4s, where it is recorded as a single channel along with the MIDI data to synchronize the listeners' reactions and the music they're hearing.

This signal is specified as a stereo signal only because the machine room mixer can mix it down to mono, since it is likely that a stereo signal is already available at the recording mixer as a by-product of the recording process. However, if it is convienient to mix the audio signal to mono elsewhere, (perhaps because, after hooking up all the slider boxes, XLR extension cable is running short), a mono signal can be used.

In fact, if cable is really running short and stereo mixdown at the recording mixer is inconvenient, we can get by with just one channel. The signal recorded on the G4 is simply for synchronisation, and only needs to be good enough to tell where we are in the music for a given MIDI time tag.

Output to the Auditorium

A diagnostic mono output signal goes from the control room mixer to the auditorium mixer. During installation and testing of the slider interfaces, programs can be run on the G4s to send audio feedback to the auditorium speakers when sliders are moved, so that installers can tell whether a given slider is working correctly without having to attempt communication with someone isolated in the machine room watching the computer screen.

But in addition...

Diagnostic Video projection of G4's Video Signal in the Auditorium (optional)

If it is possible to project the video output from a G4 in the machine room onto a screen in the auditorium, then a Max patch can be used which displays all 128 slider values simultaneously on the screen. This is in some cases a useful supplement to the audio feedback during installation and testing.

But if this is not trivially easy to do, forget about it.