Thanks guys, I did more testing today.
I can confirm that it seems like the only Cello tuning that works is Cello at 880Hz. I still don't quite get the integer offsets, is it number of scale half from the tuning frequency? Doesn't seem to make sense since the frequency of the Cello strings are 65Hz to 220Hz. Is it because there's some assumption about bass guitar in the system?
Is there another reference I can read to understand these values?
I can confirm that if I open up what few songs exist in the database for Cello, modify the tuning, and repackage, the tuner issues are fixed. Is there a chance the underlying game changed in these past few years?
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I'm not 100% sure if what I reported to @Alex360 is a bug. I see now that one must set the tuning frequency even though the preset says Cello 880Hz. That's the part that's not very intuitive. I see the advanced use case of a band set to standard tuning but at A445 for instance. I would say take no action for now and I'll report on Github if I get to something actionable. Maybe remove Cello 440Hz unless someone can explain why it's supposed to work, I double checked that I don't have something dumb like emulated bass on.
Although emulated bass would let the 1 Viola player who comes through in the next few years play cello parts on his Viola. Nice.