Pocket Beatz, created by RKCR/Y&R's digital arm Saint and Mobile Interactive Group, consists of a mobile music studio where users can play a range of beats, synths and loops to create mini tracks, which can be recorded and played back.
The application automatically links to the user's address book in their phone, allowing them to select friends and forward the content.
Users can download the application from the 'It Doesn't Have To Happen' webpage on Bebo.
Pocket Beatz will be distributed via youth-targeted media on O2 Active, which is supporting the campaign, and through Bluetooth promotions in various locations throughout the UK.
Tony Harris, deputy chairman of RKCR/Y&R, said: "Mobile is clearly a key channel for targeting a youth demographic and those who might be affected by knife crime; therefore continuing to spread the ‘It Doesn't Have To Happen' campaign message via the mobile device is a natural move for us.
"Highlighting music as a positive alternative to knife crime, in launching Pocket Beatz we hope to further engage an already strong online community, and enable young people to connect with the issue in ways most relevant to them."