Thanks for the advice, @mcgperu!
For those of you wanting to tweak with this, you can do it by adjusting the aubionotes parameters in the service script:
The current adjustment is:
ExecStart=/usr/local/bin/aubionotes -O complex -t 0.5 -s -88 -p yinfft -l 0.5
And this is the aubionotes documentation:
You can also get it from command line:
# man aubionotes
As you can see, there are different methods for onset (note-on) and pitch detection, and also a few parameters.
Aubio project is quite active, so perhaps there are new improvements or features that are not present in the Gorgona image's version, that was compiled in December. In such a case, you could update to the last version. There is a recipe script (/zynthian/zynthian-sys/scripts/recipes) that could help you with this.