Since the beginnings of movie-making, a clack board has been used to make a sharp noise with an accompanying visual. This is so the dialog of the actors (recorded with a sound recorder) can be synced to the motion picture later in a “dubbing” stage. If the clack board snaps shut but the sound takes place earlier or later, the sound and picture are not in sync. 

For sound engineering there is no visual only sound.

As described in my first book, Practical Techniques For The Recording Engineer, a well made recording consists of

• 1. A piano note in the key of the song
• 2. After the tuning note plays, a sharp loud noise (like a hand clap) to start a count-off “One”
• 3. The remainder of the count-off “two, three four, one, two three”
• 4. The song begins

The tuning note does two jobs. 

• 1. It provides an imaginary keyboard player to play a note in the key of the song.
• 2. It provides a solid note to tune instruments to should the “speed” (pitch) of the recording be changed.

Here is an example.

To make an overdub recording from anywhere in the world, here are the steps.

Remote Overdubbing A Mono Track

• 1. Record a track using the tuning note and clack/count-off as described above
• 2. Send a high-quality mp3 of this recording to the other artist who performs these steps
• 3. Open the mp3 in the free app Audacity
• 4. Add a mono track to record on
  
  
  
  
  
  
• 5. Overdub onto the new track
  
  
  
  
  
  
  
  
  
  
• 6. Save the combination of the original track with the overdub(s) to a new file name
• 7. Make a copy of the new file
• 8. Edit the COPY by deleting everything in the stereo track EXCEPT FOR the clack sound and the overdub track
• 9. Export this as an mp3 file making sure the export to mono checkbox is checked and that Quality is set to 320 kbps.
  
  
  
  
  
  
• 10. Force export to mono will combine the clack from the stereo track (with the song removed) with the new overdub mono track 
• 11. Send the exported mp3 file back to the original artist
• 12. The original artist imports the audio (the clack sound plus the overdub) into his/her Digital Audio Workstation (DAW) of the original song
• 13. The original artist drags the overdub recording up or down so that it is near the original clack sound recording, then slides the overdub recording left or right to line up the overdub clack spike with the original clack spike

DONE! The overdub is now in perfect sync with the original recording.

Remote Overdubbing In Stereo

It’s the same procedure as detailed above with the following changes.

• 1. Select Add New then Stereo Track.
  
  
  
  
  
• 2. Two new tracks will appear. Record your stereo overdub on them while listening to the original recording.
• 3. As before, save the recording with a new file name and make a COPY of the file.
• 4. Edit the COPY and remove the original recording from just after the clack sound to the end. Save this file.
• 5. When the stereo overdub is complete, export to a 320 kbps mp3 but TURN OFF (un-check) “Force export to mono.”
  
  The display will jump to Joint Stereo. That is the correct setting.
  
  
  
  
• 6. Send the stereo overdub export file to the original artist.

DONE. 

Making More Than Two Or More Overdubs

Audacity is only a two-track recorder. For two, three or more overdubs do this.

• 1. Add a mono track for each. For two overdubs (not stereo) use this technique, instead.
• 2. When the overdubs are complete, use the Mute buttons
  
  
  
  
  
  
  
  
  
  to select one overdub at a time and make a series of mono exports as described in the first section Remote Overdubbing A Mono Track.
• 3. The sequence of Mute button settings for three overdubs would be like this.

track 1     On        Mute      Mute
track 2     Mute     On         Mute
track 3     Mute     Mute      On

You will be, essentially, making a mono export for each overdub track by muting and un-muting the overdub tracks to select which overdub to export next.

Send all the overdub exports as 320 kbps mp3 files to the original creator. 

For five overdubs, there will be 5 export files.

DONE.

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