Take a look at the punch in and out functions. Basically, these functions will allow you to set where you want to record on an existing track and will automate when the recording function is turned on/off. To get oriented to the recording you would start playback of the track a few bars before where you want to record with the punch in/out function (I assume to fix something). You will hear the track up until the point where the recording starts. Then you will just hear what you are currently recording.
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