Contra 4 preview at 1-up.

"Loyal 1UP readers should be more than familiar with what Konami is showing this week; we blew out the game in far more detail a few weeks back. But! The E3 version is notable for adding in the sound effects missing from the earlier demo. Konami removed the background music (only temporarily), which allowed us to really soak in the sound effects...and they sound absolutely spot-on. By which we mean, like remastered versions of the NES games' sound effects. Every gunshot, every explosion -- even the pause chime is totally nostalgic. Which makes it perfect for this game."

Full Source: 1-up