They are due on stage today at the venue in Carver Street, Sat, July 22, around 5.15pm.
It's FREE entry and is expected to be rammed with fas who are advised to get there early to see what will be a weekend festival highlight.
And for those who can't get we are streaming it here on Facebook Live - CLICK LINK.
The Sherlocks are playing for free to thank fans for supporting their sold out shows and to preview songs off debut album Live For The moment, which is set to smash into the charts next month.
The boys - two sets of Bolton Upon Dearne brothers, singer songwriter Kiaran Crook, and drummer Brandon, guitarist Josh Davidson and bassist Andy - were planning a rare day off at the city's urban music festival.
But but The Star's Graham Walker caught up with them to persuade them to play and music promoter Neil Hargreaves was thrilled to get them on the free indoor venue at Crystal Bar, in Carver Street.
We are backing them all the way with a campaign #getthesherlockstonumberone
Live For The Moment is out on August 18. Pre-order the album and signed bundles now at http://www.thesherlocksmusic.co.uk/
Don't miss out. Tune in to The Star's Facebook page around 5.15pm at https://www.facebook.com/sheffieldstar