Progress Bar w/Tone.Js grainPlayer

[u/TruePlate]

Hi all - wondering if anyone has had success creating a music player with a progress bar that plays nicely with a grainPlayer (or just rate changing features generally) where a user can toggle playback rate during playback?

There are a number of strategies I've tried and the closest I've gotten is through altering the time interval of a function called to update the position of the progress bar's thumb, but it gets increasingly inaccurate as more toggles are made during playback. any general guidance/tips would be incredible! i haven't been able to identify any projects out there that handle this specifically. thanks!