Real-time audio recognition protocol

An audio recognition service recognizes an audio sample across multiple content types. At least a partial set of results generated by the service are returned to a client while the audio sample is still being recorded and/or transmitted. The client additionally displays the results in real-time or near real-time to the user. The audio sample can be sent over a first HTTP connection and the results can be returned over a second HTTP connection. The audio recognition service further processes check-in selections received from the client for content items indicated by the results. Responsive to receiving the check-in selections, the service determines whether a user is eligible for a reward. If the user is eligible, the service provides the reward.