It's the way you pronounce "Lager" as in beer, when you've had one too many! Gimme one more Schlager.

All kidding put aside here's what it is:
Schlager (German Schlager, literally "a hit") is a style of popular music that is prevalent in northern Europe, in particular Germany.
It is characterised by sweet, overly sentimental ballads with a simple and memorable melody.

[This message has been edited by Stephenm52 (edited 10-14-2005).]