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1.
Quite possibly the most fun, inventive, intuitive Bemani Game on the market.

It consists of 9 rounded-off, bubble-like bottons, spaced evenly apart with 5 on the bottom row, and 4 above those, spaced in between.

There are upwards of 13 different Mixed, numbered from 1-13.

Generally, there is a different theme for each mix, such as the Diner-Themed Pop'n 9, and the Halloween-Themed Pop'13. (Though I may be wrong on 13's theme.)

Many people think it would be terrific if Pop'n Music became a mainstream game, but, look what happened to DDR. Nothing good. Fan-boys screaming at their mommies for the latest version for home consoles.
Boy - "Hey, yo, let's go play DDR!"

Pop'n Fan - "Hey, fuck yourself. DDR sucks. Play Pop'n Music.
by RezOneTwoThree May 18, 2006
 
2.
Another game in Konami's Bemani series. Rather than actually simulate a real instrument, the controller is a total of 9 round bubble-shaped buttons. Capable of inflicting damage upon the player as they play the game, but probably the best game in the series. Extremely popular in Japan, but almost completely nonexistent in North America.
"Nobody in the United States has a Pop'n Music machine."
by crono June 28, 2003
 
3.
Definitively the best music game that exists.
"Would you like to indulge in some Guitar Hero?"
"No way, Pop'n Music is 100% better."
by Chris the Italian Chef August 09, 2009