The best part of any cocktail party -- after the cocktails, of course -- is the mingling. There's nothing like that charge of clicking with a total stranger, but not everyone is quick with a joke or an anecdote about Kiss or Sharpie drawings of male genitalia. Sometimes, the smart play is to hover, futz with your phone and hope to land within earshot of two funnier, more fearless guests firing away like pros.

Ted Leo and Aimee Mann are not strangers -- they were friends long before their Twitter exchanges became porn for urbane 30-something NPR listeners across the land -- but performing together as the Both, the duo they formed last year and brought to Brooklyn's Bell House on Wednesday night (Sept. 11), they have the quippy patter of smitten newbie buds still flinging A material and feeling each other out.

Their Bell House set comprised roughly a dozen songs from their forthcoming debut, a full-length due out on Matador in February, and as good as the music was, the real thrill was watching Mann and Leo interact.

They practically faced each other onstage, and by the time they'd made it through three songs -- moody stunners 'You Can't Help Me Now' and 'The Gambler' and the somewhat Thin Lizzy-esque 'Milwaukee' -- they'd also shared stories about meeting Jeb Bush at a Hilary Clinton party and taking a selfie with a statue of the Fonz.

Later, they got down on some real rock-nerd topics, like Paul Stanley's grating stage banter and the abundance of penis drawings on dressing-room walls. Apparently, some twisted individual has sketched quite the well-endowed hermaphroditic finch at a club in Cleveland, and while only traveling musicians like Leo and Mann are likely to see such things, their Inside Baseball chatter worked just fine as improv comedy.

The project was initially called #BOTH, and the fact they dropped the hashtag suggests Mann and Leo know they have a viable partnership liable to outlast social media fads. As songwriters, they haven't exactly met in the middle, but if tunes like 'Pay For It' lean more toward her hooky and acerbic '60s- and '70s-style folk-rock than his Clash-y power-pop, the two add enough to each other's sounds to suggest a genuine meeting of the minds.

"You guys are kind of awesome," Mann said at one point, surprised so many people would pay to hear songs they've never heard before.

In truth, they could have left the guitars on the bus and still nearly filled the place, and as nice as it was to hear her Oscar-nominated gem 'Save Me' -- interpolated with 'Happy Birthday,' in honor of Leo's 43rd -- the duo hardly needed to reach into their back catalogs.

That said, their encore rendition of 'Voices Carry,' a mid-'80s hit for Mann's Boston-based New Wave group Til Tuesday, was a hard and haunting reminder of the song's potency, and their unplanned version of her '4th of July,' a special request from birthday boy Leo, proved just how naturally their styles mesh.

Curiously, Leo might have done even better to suggest the X tune of the same name, as the Both function like John Doe and Exene Cervenka in reverse. Mann, the pop classicist, makes punk lifer Leo a better singer, and he scuffs her smooth edges. And to think, this musical conversation is just starting.