This concerns the effect of any residual FM-stereo subcarrier on ATRAC compression.
I have a 2 speed 2-track Revox A-77 with which I can record the output of my FM tuner at 15 ips and play it back at 7.5 ips, bringing the 19 kHz stereo sub-carrier to 9.5 kHz, well within my hearing range. I was able to validate this a couple of times while recording from the radio, I do in fact hear the high-pitched 9.5 kHz signal. In this experiment I recorded from the radio with the JE-510, dubbed that over the Revox at 15 ips, and played it back at 7.5 ips.
Here are the results:
When there is no modulation (silence being transmitted) I can clearly hear the sub-carrier at half frequency. Any modulation will remove it however. For example with speech, it appears during the pauses, and disappears between them.
This would indicate that :