Avoiding unnecessary reference data re-generation
Avoiding unnecessary reference data re-generation

Previously, these constants/reference data were re-generated for
each note in a serialized song, each time a serialized song was
generated. (I.e., a lot of times during normal usage of the app).
However, this data never changes so there's no reason to do so.

Although I don't think this had a practical negative impact, it
seems like an easy thing to avoid.

jstrait/jssynth,jstrait/jssynth