Should the song attributes "Kasane Teto" and "Kasane Teto SV" be separate?
Currently there are two song attributes that I think could be merged: Kasane Teto and Kasane Teto SV. I understand that there is a technical difference between the two -- the former is for UTAU and the latter is for SynthesizerV -- but I'm not sure if the difference matters to those looking for songs sung by Kasane Teto. I think it would be easier to find songs sung by Kasane Teto if the two attributes were merged, since they more or less refer to the same singer. That said, I am not familiar with how Kasane Teto fans perceive the difference (if any) and with vocal synthesizers in general to definitively merge the two.
I feel as though their difference is negligible. In some cases it could even be hard to tell which a song is using, adding to confusion when tagging. They should be merged, in my opinion.
It was a conscious decision to not implement multiple inheritance for song attributes since combination tags don't need to exist here. I hadn't really considered this sort of cases, and it's making me reevaluate this decision since I think it could help here. Open to hearing your thoughts.
I think that song attributes do not need multiple parents for the reasons you have mentioned. Additionally, I cannot think of another example that would also benefit from having multiple parents, and therefore motivate allowing attributes to have multiple parents. If such a change did happen, I think at that attributes should be stricter than tags in terms of the number of parents, and that multiple parents would be reserved for outlier cases like this. However, I cannot say if a merged Kasane Teto attribute should be parented to UTAU or SynthesizerV (or some other parent) in the current one-parent rule.
If anyone has another example that could have multiple parents (it does not have to be a vocal synthesizers that exists between 2 softwares), I would love to hear it.