Musicians unite for 12-12-12 Concert for Sandy Relief - live stream
Note: This live stream has now finished and the event is being rebroadcast.
The Rolling Stones, Coldplay frontman Chris Martin, The Who, Kanye West, Eddie Vedder and Alicia Keys are also among those on the bill, and McCartney is tipped to join forces with Nirvana members Grohl and Krist Novoselic as the pair play together live for the first time in almost 20 years.
Columbia Records is also releasing an album featuring 24 tracks from tonight's show.
Proceeds from the show and sales of the album will benefit the Robin Hood Foundation's Relief Fund, a charitable organisation which helps those in poverty in the New York area.