Our Heartstrings Stuffy has a velcro pocket in the back where your heartbeat recording will be inserted and can be easily played with the push of a button. The speaker can be removed to charge using a USB cord provided with purchase (no real batteries to worry about for babies/kids!). Build your own Heartbeat Project in the shop to add anything you want to your stuffy! Other songs/voice memos can be added to speaker which holds up to 30 minutes of playing time.