Fall Out Boy & Foxes performing 'Just One Yesterday' together live at Reading Festival 2013.

Foxes joined Fall Out Boy on-stage at Reading Festival 2013 today, to perform their song 'Just One Yesterday' together live.

Ah, what I wouldn't give to have gotten to see this live. Louisa's vocals are flawless!

Watch the performance below...

P.S. Click HERE to read our latest Fall Out Boy interview.