Here's the mention from Screen Daily article:
Knightley in for Johansson on Exclusive's SongA summer shoot in NYC is planned for this film, according to The Playlist.
EXCLUSIVE: Keira Knightley has replaced Scarlett Johansson on Can A Song Save Your Life? which Exclusive Media is financing, producing and selling in Cannes.John Carney, the filmmaker behind the hit Irish musical romance Once, will direct the story about a singer who moves to New York with her boyfriend only to be dumped by him and subsequently discovered by a producer. Hailee Steinfeld also stars. Johansson is understood to have left due to personal reasons.
In other KK movie casting news, she is no longer in talks to star in a new Nicholas Sparks' film adaptation of Safe Heaven.
I previously posted here recently that Keira Knightley was said to star in Nicholas Sparks film adaptation 'Safe Haven' as Twitch reports that Keira Knightley is in early talks to star in Lasse Hallström‘s adaptation of Nicholas Sparks‘ novel Safe Haven.
Apparently, Variety reported that Josh Duhamel, the Transformers star was recently in negotiations to lead the adaptation of Sparks’ Safe Haven. Duhamel would play the widowed store owner, but producers are still trying to fill the female lead role. So, KK is no longer in talks to star in this film.