Sono presenti due pianoforti e due pianisti uno di fronte all'altro.

"dueling pianos": usually on stage with two grand pianos, each played by a professional player who sings and entertains; humor and audience participation are prevalent. Usually these types of piano bars have substantial sound systems, and most of the songs performed are rock and roll, "classic rock", Top 40, R&B or country, sometimes played by request. The format is based on dueling piano entertainments offered at Pat O'Brien's Bar in New Orleans, Louisiana, and was popularized in 1986 at Alley Cats in Dallas, Texas.[citation needed] Numerous popular clubs offer the sing-along format, while Howl at the Moon Piano Bar and the The Big Bang Dueling Piano Bar feature full performance shows, often with singing and dancing by their wait staff.
http://en.wikipedia.org/wiki/Piano_bar

A dueling piano bar is typically a small nightclub that centers around two grand pianos positioned back to back with two pianists facing each other. The pianists play songs based on requests from the audience. Patrons write their requests on request forms or any piece of paper they can find and put them on top of the pianos. The piano players then get to work on playing as many requests as they can - usually starting with the requests that have cash attached to them. Cash tips that accompany the requests range from $1 to $100 depending on how badly the patron wants to hear their song - or how drunk they are.

--------------------------------------------------
Note added at 12 min (2011-06-30 16:41:30 GMT)
--------------------------------------------------

http://duelingpianoskc.com/duelingpianobar.html