RoTunes is a app given by a gamepass. It allows you to play any music ingame. The current price (as of 4/3/2018) is R$150. You can buy this with $1.99, but you must use Rixty (a payment method) to buy it.
The app allows you to:
- Import Roblox songs & sounds
- Save songs & create playlists
- Play individual songs or playlists on loop
- Dynamically adjust volume and shuffle songs
- Lastly, Firebrand1 will (eventually) allow you to sync your phone to your sound system and play your playlists for your friends at your house! The sound system will put you a few grand in the hole, though.