'Teenage Dream' beauty Katy Perry has revealed that the next preview from her upcoming album 'Prism' will be unveiled at the end of this month. 

She has already treated her fans to 'Roar' along with a new track from the cut, entitled 'Dark Horse', and has now promised that a song called 'Walking On Air' will debut on September 30 although it won't be released as a single. Writing on Twitter (September 17) she explained:

"Morning kittens. Hope you are enjoying #DARKHORSE. It's just a TASTE of what my PRISM has in store for you... Mark your calendars for the next #PRISMPREVIEW on SEPT 30 when you can hear/have the new song "WALKING ON AIR..." before the record hits."

She then returned to the site and added: "Remember these are NOT singles, just tastes to enjoy! #ROAR is still ROARING & 2nd single from PRISM will not be announced for some time... But don't you worry... I promise you'll like it!"