[unwind]

Uh, speaking as a mere human, can you actually hear the music shift in tempo from 99.5 to 100.5 bpm? Or does this become apparent when using tools/mixers/whatever to work with the audio stream?

I just quickly tried this on Google's built-in metronome widget (TIL) [1] and I can't hear the difference between 99, 100 and 101 bpm. However, the switching is discrete (the audio stops and restarts) which probably makes it much harder to detect change, of course.

Just curious, not trying to question your comparison of course.

[1]: https://g.co/kgs/Qqdz4d

[rfreiberger]

I personally cannot tell, if I was mixing vinyl I honestly would never have known about this. But using a digital vinyl system like Serato which displayed the bpm as 100.0, it's very apparent the tracks will fluctuate. The other issue is since your turntable is keeping time, two of them playing the same BPM, say 100BPM can drift 1BPM in theory. That's a large number when playing slower songs like hip-hop, and easily cause drift within 15~30 seconds. It's not a big deal, most dj's ride the pitch fader but it's worthy of a mention that the Technics 1200's are just over engineered.

[Intermernet]

If you're trying to beat match 2 tracks, and they're playing together for more than a few seconds, this becomes frustrating. A test I do is play 2 copies of the same record simultaneously and see how long it takes to noticeably go out of sync, given all other variables matched as closely as possible.

[dopamean]

I can definitely hear it when I'm performing. However even as a dj if I'm on the dancefloor having a good time it's mostly imperceptible.

[tinus_hn]

You might not notice the speed change but most people will definitely notice the accompanying pitch change.