It's the next in Apple's "Live From London" series of in-store live events.
It's understood these at present monthly events are scheduled to increase in frequency during the year.
Fretwell's performance will be recorded and made available for download through the iTunes Music Store the following week. The artist joins a line of performers who have appeared at a Live From London event: James Blunt; Tom Veck; Stereophonics.
Fretwell (23) grew up in Scunthorpe and studied at Salford University where he became a full-time musician (and failed to graduate). His first album, 'Magpie', was recorded at Abbey Road and is available on Fiction Records.
Space is limited - just 250 tickets will be available for this free event. The music is likely to start between 7pm-8pm on August 2.