Alphabeats: PC Master Edition is featured in the Adventure Beats bundle from Groupees! It's the only way to play Alphabeats on PC right now. Included with the $1 purchase are three other games and albums, with four extra if you pay at least $2.
The Adventure Beats version of Alphabeats features a fully playable version with twenty songs. It supports Mouse, Keyboard, and Joystick controls. Leaderboards, achievements, and robust PC options aren't in there yet, but they will be if Alphabeats game is approved for Steam, so keep spreading the word!
The bundle is available until April 18th.