Let's Tap Cheats
Complete the Gem Game mode in Visualizer to unlock Ocean Mode.
Unlocks Songs 17-20
Complete all the tracks in Rhythm Tap with an S ranking to unlock songs 17 through 20.
All Game Modes
To unlock all the bonus game modes as well as the extra songs without fulfilling the requirements you just have to have save data from the WiiWare game, Let's Catch on your console.
Complete the Alchemist Mode in Silent Blocks to unlock Binary Mode.