Recorder of the Bard

Rod Recorder of the Pact Keeper Bard
Rod Recorder, uncommon (+1), rare (+2), or very rare (+3)
(requires attunement by a warlock bard)

While you are attuned to and holding this rod recorder, you gain a bonus to spell attack rolls and to the saving throw DCs of your warlock bard spells.  In addition, if you have a tools proficiency with this musical instrument, then you gain a bonus to your proficiency bonus on any ability checks you make to play music with the instrument.  The bonus is determined by the rod's recorder's rarity.