To go along with a homebrew Artificer subclass that I've recently asked about that is very focused on playing musical instruments, I've created a thematically related Infusion, that any Artificer should be able to choose, starting at 2nd level when the Infuse Item feature unlocks:
Item: A musical instrument (requires attunement)
While playing this instrument, a creature gains +1 on ability checks related to their performance. Spells cast with this instrument as a spellcasting focus gain +1 to their spell save DC. These bonuses increase to +2 when you reach 10th level in this class.
Is this closely inspired by the Enhanced Arcane Focus, but sort of suspect that increases to spell save DC might be more valuable than a bonus on spell attacks (I expect the bonus to performances with the instrument is mostly a ribbon, and not important to balance concerns). The spellcasting DC bonus only helps bards and Artificers (either of my subclass, or other ones that infuse the instrument themselves and can thus use it as a focus), not other spellcasters.
Is this infusion balanced against other infusions available at 2nd level? Would it be better if you gained access only at a higher level? 6th, 10th and 14th levels have precedent, though the latter two only for the Replicate Magic Item infusion.