Inspired by the concept of geocaching. Use Shazam or a similar, specialized app to identify (catch) specific, "hidden" songs played in certain venues at certain times.
An incentive for people to go to specific venues/events, hence - a marketing strategy. Provide prizes for winners to incentivize it even more.
In addition to the location-only factor used in geocaching, this introduces time factor to the game, also, instead of finding material objects, one moves to an artistic realm to "look" for music.
The game involves memorizing music and trying to recognize it later, this trains your ear and your memory.
The game initiator (a Dj, event organizers, club owners, etc.) posts a short song excerpt, which you are supposed to memorize, on the app sometime before the event. At the event, when dancing/listening to music you should "look" for the song from which the excerpt is taken. Once you hear something similar being played, try shazaming it. Once the app identifies the song it tells you whether it was the correct catch or not.
The app has access to a register of all the events that have "hidden" songs in their repertoire. It knows which event/venue you're at by reading your location data and time. Additionally, you could check in at a specific event by scanning a QR code at the entrance.
To make things more difficult, the initial excerpt can be mixed with a sound signal (eg. ultrasound) that you wouldn't hear but the song identification app would register and it would block it from identifying the song. This would prevent you from identifying the song earlier, and listening to all of it, and make it more difficult to cheat by playing the already recognized song through your own device at the venue, shazaming it, and pretending that you "caught" it.
Also, the excerpt could only be available to listen to online and only till the time of the event so you wouldn't go around playing it over and over and comparing each song played at the event to it. This would make you train your ear and your memory instead.
Just about any song could be selected for a cache, but it would be better to use the least known songs (fresh releases or even unreleased ones). This would both help prevent cheating and make things more interesting for the participants. It would be a perfect way for a music producer to present their new song publicly for the first time.
Since currently Shazam is only capable of identifying recorded music, the concept I'm suggesting wouldn't work for live concerts/musical performances. So the main type of venue that could make good use of this idea is clubs. There's no reason why just about any establishment playing recorded music couldn't use it - bars, ball venues, cafes, etc., it's just that with clubs it's more interesting since Djs prepare their sets specifically for each event they're playing at, so it's more "organic" or "live" in that sense than simply putting on some playlist with a "hidden" song in the middle and forgetting about it.
The game seems interesting enough in itself, but to motivate participants even more the initiators could give prizes after the event to all those who successfully identified the musical cache(s). To limit the number of prizes, only those who "caught" the song(s) first could get rewarded.
I believe this concept can be expanded and improved in many ways, could you offer some ideas on how to do it?