Click the song you want to play to hear it. Click the backdrop to stop it click to button to go to the next page and click it again to go the the previous page. THe secret has been found
Credit to pococikapusta for sans and frisk and credit to X-Undyne-X for the button. From youtube: sans the skele,yuki yuki,videogame remixes,The Musical Ghost, Elu Tran, elizabettha-chan Undertale:Toby Fox
