Four Roses has been one of the bourbon geek darlings over the last dozen years or so. There's the heartwarming story about how the distillery was a powerhouse for most of its life, was then neglected for decades while the name was used to sell terrible blended whiskey in the United States, then returned to glory when it was purchased by a Japanese company (which is the country where most of the good stuff had been going in the meantime).
One of Four Roses' claims to fame is that they produce whiskey from ten different recipes, which are the intersection of two different mashbills (20% rye and 35% rye, with the balance made up with corn and malted barley) and five different yeast strains. Only one of these recipes, OBSV (35% rye, delicately fruity yeast) is used for their Single Barrel. Each barrel is picked, then proofed down to 50% ABV, and bottled without coloring or chill filtration.
Four Roses Single Barrel
Nose: fairly closed at first, opens to nutty caramel, simple syrup, vanilla beans, solid slab of oak, milk chocolate/cocoa powder, pears, musky fruit, vinous notes, and berry overtones. After adding a few drops of water, the nutty caramel dominates the nose, the oak is more sawdust-y, the fruit/berry/vinous notes are tighter and less bright, while the corn fades to reveal more rye.
Taste: corn and caramel sweetness sweetness throughout, tempered by rich polished oak with a vinegar edge in the middle, with berries, floral notes, and rye spice in the background throughout. After dilution, the sweetness is significantly diminished as the oak tannins gain ground, though there is a big burst of berries at the beginning, and some apple and vanilla notes around the middle, fading into more pronounced tannic bitterness at the back.
Finish: moderate oak and grain, fresh apples and berries, rye spice
The standard release single barrel has clearly been chosen for mass appeal. This is a very classic bourbon, with strong elements of corn sweetness and oak, adorned with rye spice and berries. Everything you would expect is here, but the flip side of that coin is that it doesn't offer any flashes of brilliance either. It's very enjoyable and very solid, but it doesn't quite hit the high notes that some of their other recipes hit. I would put it in a similar category to Blanton's, another single barrel bourbon that has very classic notes.