Making The Recording

WARNING: This page is part of our multichannel audio player 1 project. If you are considering this project, read all Related Pages before you start!

NOTE: This project is has been discontinued, and is provided only for historical reference. Please see multichannel audio player 2 instead.

Making The Recording
Recording Details
Related Pages

Making The Recording

Use A Computer

The recording necessary to drive this multichannel player is best created on a computer and burned onto a CD.

Tape recordings could be used, but tape machines sometimes speed up or slow down a little, changing the tones. The electronics may not be able to reliably recognized control tones on a tape.
The audio channel must contain all of the stuff that will be heard - no matter who sings it. If you are starting from a stereo source, you must mix the left and right channels together.
The control channel must be precisely constructed with tones that indicate who is and who is not singing at any given time.

All in all, a computer is the easiest way to do this.

It's still a complex task, so we have fallback plans.

Why Bother?

You may be tempted to point out that, since a computer is involved in cutting the CD, why not just have it control the performance?

You could shove several sound cards in a PC and have it play independant channels. Or you could play a sound track, while relays driven from a parallel port control who gets to sing.

Yes - these things would work just fine. But now you have to have the computer nearby, up, and running as long as the show is on.

In our case, we put a little more effort into preparation of the performance, in order to play it back on a rather cheap machine. And since the player is inexpensive, you can have several throughout your haunt, instead of a larger computer that would probably have to reside at a central location.

Lead-Out

I love the idea of a bunch of pumpkins or skeletons singing in harmony. But I don't love the idea of the same some playing again and again all night long.

I think that it's a good idea to have several different songs to be performed. And I also think that the performances should be on-demand, not continuous.

While thinking about thunder on demand, I decided that the best way to do something like this was to create a CD with several tracks and a long period of silence after each track. If you should leave the CD player alone, the player will eventually run through the silent portion and you will get another performance - but with a gap between. And if you need another performance right now, you hit "next track", and it starts right away.

This can be done either by adding silence to the end of each track in the recording, or by telling the CD burning program to include lead-out time.

Burning

When it comes time to burn the performance material to disk, I would suggest writing in standard audio disk format.

If you have a player that plays disks full of MP3s, you might try writing that format, but make sure that you test it carefully - if the tones don't come out just right, the multichannel decoder won't function.

Make sure that the speaker audio is on the right channel of the stereo recording.

The left channel of stereo recording contains either "animation audio", DTMF tones, or both.

We suggest that each performance number be written to the disk with a few minutes of silent Lead-Out.

Be sure that all of the performance numbers are normalized to a uniform volume, on both channels. When playing this back, you don't want to fine-tune the volume for each number!

Recording Details

The multichannel player has numerous operating modes, which support many different types of recordings. This flexibility offers us many fallback plans in case the recording is not produced in time, or is damaged at the last minute.

This section outlines the procedure necessary to produce a recording for each of the various fallback plans.

Plan A...

Capture on the computer a recording of the musical performance you wish to replay through this system.
If the recording is stereo, mix it down to mono. Discard everything else - you just care about the single mono channel. This is basically the "speaker audio" track (we'll call it SA).
Set up your computer to record from a microphone. Set things up to play some version on the musical number in such a way that is doesn't go into the microphone. You can use earphones or earplugs.
Play the number, while you sing along into the microphone, capturing. When this is done, you should have two channels on the computer: a mono version, with professional singing and instrumental accompaniment; and your singing (we'll call it V). It doesn't matter how good your vocals sound - nobody will hear them. This is the basis for your "animation audio" channel.
Create a new channel that contains just a single tone, at 3 kHz (we'll call it T). Make it as long as the V track.
Tell your software to take the volume envelope of V and apply it to T. This is a new form of the "animation audio" channel that is safe to mix with DTMF signals.
Decide which parts of the song are to be performed by which voices. Edit the T channel, inserting DTMF tones to turn on and off performers.
Burn SA and T to a CD as stereo: SA on the right, T on the left.

Plan B...

Capture on the computer a recording of the musical performance you wish to replay through this system.
If the recording is stereo, mix it down to mono. Discard everything else - you just care about the single mono channel. This is basically the "speaker audio" channel (we'll call it SA).
Make a copy of SA. This is basically the "animation audio" channel (we'll call the copy AA).
Edit the AA channel. Whereever there is material that is not to be voiced by a performer, make the amplitude zero.
Create a new channel that contains just a single tone, at 3 kHz (we'll call it T). Make it as long as the AA track.
Tell your software to take the volume envelope of AA and apply it to T. This is a new form of the "animation audio" channel that is safe to mix with DTMF signals.
Decide which parts of the song are to be performed by which voices. Edit the T channel, inserting DTMF tones to turn on and off performers.
Burn SA and T to a CD as stereo: SA on the right, T on the left.

Plan C...

Capture on the computer a recording of the musical performance you wish to replay through this system.
If the recording is stereo, mix it down to mono. Discard everything else - you just care about the single mono channel. This is basically the "speaker audio" track (we'll call it SA).
Create a new channel that contains just silence (we'll call it T). Make it as long as the SA track.
Decide which parts of the song are to be performed by which voices. Edit the T channel, inserting DTMF tones to turn on and off performers.
Burn SA and T to a CD as stereo: SA on the right, T on the left.

Plan D...

Capture on the computer a recording of the musical performance you wish to replay through this system.
If the recording is stereo, mix it down to mono. Discard everything else - you just care about the single mono channel. This is basically the "speaker audio" track (we'll call it SA).
Set up your computer to record from a microphone. Set things up to play some version on the musical number in such a way that is doesn't go into the microphone. You can use earphones or earplugs.
Play the number, while you sing along into the microphone, capturing. When this is done, you should have two channels on the computer: a mono version, with professional singing and instrumental accompaniment; and your singing (we'll call it V). It doesn't matter how good your vocals sound - nobody will hear them. This is the basis for your "animation audio" track.
Burn SA and V to a CD as stereo: SA on the right, V on the left.

Plan E...

Capture on the computer a recording of the musical performance you wish to replay through this system.
If the recording is stereo, mix it down to mono. Discard everything else - you just care about the single mono channel. This is basically the "speaker audio" channel (we'll call it SA).
Make a copy of SA. This is basically the "animation audio" channel (we'll call the copy AA).
Edit the AA channel. Whereever there is material that is not to be voiced by a performer, make the amplitude zero.
Burn SA and AA to a CD as stereo: SA on the right, AA on the left.

Plan F...

Just shove in any old CD and play it!

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