This 12th entry was created by zarxrax (author of DSLearnJ)
Here is his description:

This is a mockup of a rhythm game that utilizes the Nintendo DS’s touch
screen in a unique way. While most rhythm games focus on beat, this one
focuses on the pitch of the music. Lines will come across the screen,
and you move a disc up and down along a vertical line, attempting to
follow the path as accurately as possible.
Your score is determined by how accurately the path is followed. The
disc has a hole in it’s center. When this hole is on the path, then you
get the maximum points. If the disc itself is touching the line, then
you get less points. If the disc is entirely missing the path, then this
will cause the life meter to decrease. Once the life meter is depleted,
you lose the stage and must retry. In addition to merely following the
path, each separate line in the path has a rounded tip at its beginning.
The player must lift the stylus from the screen and then press down on
these rounded tips. Again, how accurately you press it determines how
many points you get, but these rounded tips also serve the purpose of
adding a multiplier to your score. The multiplier can keep increasing as
long as you keep a chain going (no misses). Once the chain is broken,
the multiplier resets.
The top screen displays the life meter and your score, and possibly
other info such as the length of your chain, and the current score
multiplier. It may also display a visualization to the music, but this
is not necessary. There should however, be some sort of visual feedback
as to how accurately you are following the path at any given moment. For
instance, the screen may have a green backdrop when you are doing
perfect, and change to red when you miss.
My mockup is designed for a left-handed person, but the game should have
an option to flip the gameplay, so anyone can play.
Finally, there would also need to be a level editor which can run on the
PC. It would be a fairly simple editor, which allows one to load the
audio, display some information such as a wavform, and allow you to set
the BPM (determines how fast the level will scroll across the ds screen)
and then plot some points which will make up the level.