About the API: You need to use any program like Postman to be allowed to do requests like delete or add a song, search an user, obtain a complete list of users or songs, etc.
If you want to obtain an array with the complete list of songs in the DB:
http://localhost:3030/getSongs
If you want to obtain an array with the complete list of users in the DB:
http://localhost:3030/getUsers
If you want to delete an user from the DB:
http://localhost:3030/delUser
If you want to add an user into the DB:
http://localhost:3030/addUser
If you want to add a song into the DB:
http://localhost:3030/addSong
If you want to remove a song from the DB:
http://localhost:3030/delSong