Yamaha MT8X Operation Manual page 20

Notes
Be careful not to record the tape playback signals input to a channel onto a track which has the same number
with the channel. This will cause an oscillation.
Various other methods of monitoring recordings are available, in addition to those described above.
Be careful not to monitor the playback signals on tracks and the signals made by mixing (ping-ponging) them at
the same time, otherwise monitoring cannot be done properly.
The overuse of ping-pong recording may deteriorate audio sound quality. Ping-pong recording a recorded sound
should not be carried out repeatedly.
Ping-pong recording onto adjacent tracks within the same block of the record/playback head should be avoided.
This can cause audio signal oscillation.
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