It is considered one of the greatest cellos in the world, a beautifully preserved product of Antonio Stradivari that was once owned by Nicolò Paganini and most recently by Bernard Greenhouse, a founding member of the Beaux Arts Trio. Mr. Greenhouse played the cello for a half century, and after his death last year, his family decided to sell it, hoping it would go to a deserving musician.

They got their wish, and a record price.

Christopher Reuning, the rare-instrument dealer in Boston who handled the sale, said on Saturday that the cello had been sold last week for “a fair bit above” the minimum bid price, which was slightly over $6 million. He declined to specify the exact amount. Mr. Reuning said the amount exceeded the previous record of $6 million.