Thank you so much for your comment!
You are 100% right on the difficulty ramping (especially the solo!) This is something we would have tried to smooth out better with more time, but wanted to give an overall taste of what a game like this could end up becoming. Also, we discovered after the jam closed that there's a bug with one of the 'song transformation' options in the second last round where it doesn't properly add the 5th lane - so unfortunately I think you didn't get the full progressive experience.
For a final product, I think we might implement a 'never ending' mode and/or a death system or something else to encourage replayability. But for the game jam we wanted to make sure everyone could make it to some final version of the song. There would also be more time spent on the note charting and more songs with difficulty levels to make sure everything meshes together better.
Thanks again for your comment! Really glad you enjoyed the music and the game!