A general comment: Your mention of "tempo" suggests you are using a music track, I think? If that audio is "locked" to a video track, and you speed up the video, the audio should speed up BUT it will very quickly "mute" if the speed increase is anything more than a very small amount. Similarly, if you slow the video more than a small amount, the audio will mute.
My problem is when i slow the video down, the pitch of the audio remains the same. In example a slowed down rally car still sounds the same than before. Just a bit more stuttering. I would like the sound to be at lower pitch. And if speeding the video, the audio pitch should rise as if the car was on helium.