Many here have speculated for years on the elements that make a bourbon (and a great bourbon). One is yeast, since yeast, while not a flavor enhancer (but rather an ingredient to ferment sugars into alcohol) has undeniable flavour and it carries over into the distillate.
Recently I sampled, through no intention to taste them as a group, Weller Centennial made in Louisville (UDV, now Diageo) and Old Charter 12 years old (made ditto). There was a clear connection between the two and I realised it is a mineral and, well, vitamins flavor - exactly like in all the George Dickels I've had (except one from an early 60's "powderhorn", but never mind).
All three whiskeys, made by one company, had this common taste even though Weller was (and is) a wheat-recipe bourbon and the Charter a rye-recipe bourbon and 12 years old. Dickel is charcoal-leached prior to barreling and ostensibly a different style again.
What unites these 3 is, in my opinion, the yeast used to ferment their mashes.
UDV must have been using the same yeast and I further conclude this Weller Centennial was made at old Bernheim, not S-W since S-W whiskeys don't have that taste.
I must say I can't recall this taste in I.W. Harper from Louisville, maybe it had a different yeast though.
Anyway I wasn't looking for this connection but it is unmistakeable I think and shows the effect arguably of a common yeast. I don't think any other factor can explain it since e.g. Dickel was aged in a different State let alone microclimate.