Interesting N.B. = tempo equation typo gets playback stuck on q=500

A typo in tempo equation lead to an interesting result. Starting from tempo w=54 (working from 16c mensural notion so this does make sense), the tempo equation I needed was w=w. for a 3/2 proportional tempo increase. However, I accidentally typed h=w. which is a 3/1 increase and it causes the quarter note equivalent tempo to exceed 500 BPM. The 3/2 increase works fine as this is 324 BPM in quarter-note tempo, but my tempo equation typo instructing 3/1 increase would equal 624 BPM which evidently crosses a 500 BPM limit. That’s fine, but I just want to report that once this happens, the playback does not recover. It is stuck on 500 BPM for any position, any flow. Only a close and reopen of the file will reset.

A typo is a typo, so mea culpa. Just reporting application behavior under this circumstance.

Demonstration attached. Cheers.
Tempo_equation_typo_test.dorico (1.0 MB)

Apologies: I do see there is not a q= limit at 500 per se, as a quick test starting with q=500 explicitly as a tempo, then using my w=w. tempo equation does in fact play at q=750 and even my typo h=w. will play at q=1500! So I did not describe the issue exactly.

Looks like the slippage has only to do with cases of starting with a tempo expression not based on the quarter note. I did try starting with h=250 instead, and playback did get stuck afterward on q=500.

I had something similar happen a while back - the whole project got stuck at a fast speed and ignored all tempo marks. But I didn’t have time to reproduce it. Restart Dorico and the problem went away. There is definitely a glitch there. (I’m still on D4).

Should you run into this in future, you don’t need to restart Dorico or even reopen the project. Instead, toggle the “follow tempo” mode in the transport and set a fixed tempo, play back, then toggle “follow tempo” mode back on, and playback will resume at the correct tempo.

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