Mario plays along to the music in Super Mario World (not Super Mario World’s music)
This is from a SMW (Super Mario World) romhack called Automatic Mario SE. (I presume it stands for Special Edition) I give full credit to the makers of this romhack. At one point, the song is Beware The Forest’s Mushrooms from Super Mario RPG! And at another point, the song is Here We Go! from SMW!