The Problem:

When you have a 4-track, you'll constantly find yourself running out of room on the tape.... Every home recordist has said, "I wish I had 2 more tracks left."   The most obvious cure for this is to enlarge your studio to 8 or more tracks.  If you're a poor musician (and I bet most of us are) this may not be possible.  The other possibilty is to creatively use "track bouncuing" to allow you to free up tracks and add more.

The Internal Bounce:

Bouncing means mixing down 2 or 3 tracks of your tape onto the 4th (blank) track, so you can use the original 3 tracks for something else.  With a few bounces, you can create a virtual 8-track.  The tracks you're recording are shown in green, the track you mix to is shown in yellow.  Track numbers in grey are not being used in this step.

Record onto tracks 1,2 and 3 on your deck.   Playback the 3 tracks, and mix them down and record them onto track 4.  So far this is 3 tracks of recording/

• 1 + 2 + 3 -> 4

• 1 + 2 -> 3  (4)

• 1   2   (3)   (4)

Oh, one last thing about bouncing, very obvious, but I see some confusion about this nevertheless: all of the bounced tracks by themselves will be mono, because you're mixing down to ONE track in each bounce stage.

The External Bounce:

So, you like the idea of bouncing, but not necessarily the thought of a mostly-mono mix, huh?  If you have a decent 2 track recorder (Minidisc, DAT, HiFi VCR, CD-R, DAW) you can make an external bounce and preserve your stereo tracks.   You could also use a cassette deck, but I prefer not to bounce to tape.  With an external bounce, you record the bounce on a different stereo recorder, rather than onto a spare track on your multitrack.  There is more re-recording with this method, so a high quality 2 track is essential to get good results.

When using an external deck for bouncing, you can use every available track on your multitrack machine.  You record all 4 tracks, then mix them to your mixdown deck.  You can then rerecord this mix back into tracks 3 and 4 of your multitracker.  Since you're using 2 tracks for your bounce, you can maintain a stereo image. At this step, I recommend using a fresh piece of tape, rather than rerecording over the old version.  New tape will give you the best sound quality.

• 1 + 2 + 3 + 4 -> 2trk deck
• Copy 2trk -> 3 + 4

• 1 + 2 + 3 + 4 -> 2trk deck
• Copy 2trk -> 3 + 4

• 1 + 2 + 3 + 4 -> 2trk deck (final 2 track master tape)

It takes some experience to do the bouncing right, because you can't change the individual levels of the bounced tracks after bouncing, of course. And in the total mix the levels of the individual instruments often sound different from when you hear them with some tracks muted (or in this case, without the not-yet-recorded tracks). But do it a few times and you'll get a good idea of how the level balances should be.

Consider that the sound quality of the tracks deteriorates with each bounce. Cassette is famous for losing the high frequency information with each generation.  Also, each copy adds more wow and flutter to the resulting mix.  So use the instruments that aren't so critical to loss of highs (like the bass) and wow & flutter (like the rhythm guitar or a male voice) to do the bouncing. YMMV, just experiment and listen what sounds best.  It is also useful to boost high end when making your bounces to help account for the loss that will surely occur iin each subsequent generation.  The first bounce will need the most high frequency boosting (3-4 dB or so, depending on the deck), and the second bounce will need less of a boost (maybe 1-2 dB).

If you want to know more about bouncing, feel free to contact the author Erwin Timmerman.