Barcelona - Cameroon midfielder Alex Song signed a five-year contract with Barcelona on Monday, bringing an end to his time with English Premier League club Arsenal.
Song posed for the traditional photo in front of the club's insignia before passing a medical examination and meeting with Barcelona President Sandro Rosell.
The Spanish club paid Arsenal €19m for Song. Arsenal sold striker Robin van Persie to Manchester United earlier this week for £24m.
Barcelona coach Tito Vilanova said he was impressed with Song's versatility.
"(Song) can provide us with a lot of things. He's very good, he recovers the ball well and then can do good things with it," said Vilanova, who sees Song sharing time with Sergio Busquets as a defensive midfielder alongside the more attack-minded Andres Iniesta and Xavi Hernandez.
"Busquets can't play every game of the season so Song will be a great addition," he said. "And he can also play in the center of the defense. With him we'll have more alternatives (because) he can play in three different positions."
Song is Barcelona's second signing this summer after defender Jordi Alba, who joined from Valencia.
Barcelona thrashed Real Sociedad 5-1 in their Spanish league opener on Sunday.
On Thursday, Barcelona host rivals Real Madrid in the first leg of the Spanish Supercup.