Virtual tracks:
Press the Track Edit button. Use the cursor arrows to move down to highlight Exchange and hit the Enter/Yes button.
You'll have two sets of numbers representing the channels/tracks. Use the jog shuttle to select what tracks you want to exchange. To move left/right within the display, use the cursor arrows.
A good idea is to write down what tracks you exchange. It gets pretty messy after a while.
Virtual tracks are used to store different takes of a performance, or they can be used as extra tracks to be recalled when you bounce or mix down to stereo tracks.
Scrubbing:
This is for editing. Stop the VF anywhere in a song where there is sound recorded and press the Wave Form Scrub button. You'll be asked to select a track. Select one that has sound at the location you stopped the recorder, and that tracks sound wave will show up on the display.
Using the jog shuttle you can navigate 'in' your sound wave with extreme detail, down to fractions of a second.
Scrubbing is great for setting Start, End and To-points when erasing, copying or moving audio. Set the points with Shift/F1;F2 & F3, then Exit scrub mode, go into Track Edit, and when you select Copy etc, these points will pop up.
It's also really useful when you want to set precise In and Out-points for Auto Punch.
If you set the tempo of the song before you start recording, setting points and marks become really easy.
Sometimes, when people scrub audio the first time, they think it sounds weird (i definitely did...), but remember, it's almost like when you're using slow motion on a VCR - only this is much, much slower.
The manual:
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Hope this stuff helps.