Bring your own .miniusf/.usf files by dropping them onto the N64 console (you'll have to drop the .usflib first - before dropping the song files that use it). Respective files can be found for example on modland.com.
2018 by Juergen Wothke (The source code can be found here.)
The music that is currently played as an example is from the game Wipeout64 (Copyright by Psygnosis). May it bring back some good memories of that franchise and I hope there are no objections to using it here.
Please use the below controls to navigate between the songs that you have dropped on the player: