Credit: Michael Becker/Fox

Fox’s American Idol performance finale was down slightly in the ratings from last year’s all-time low.

Tuesday’s episode delivered 20 million viewers and a 6.2 preliminary adults 18-49 rating, down 7 percent from last season’s final performance show. The performance isn’t unexpected given that Idol has been tracking slightly below 2010’s run all season, itself an accomplishment given the age of the show and all the changes to the judging panel.

Still, last night marked the lowest rating ever for a performance finale of American Idol. Last year had a 6.7 demo rating, 2009 an 8.6 and 2008 was at 10.1.

The Glee finale was strong, earning 12.1 million viewers and a hearty 4.6 rating — the most-watched episode since Week 2 of the season (excluding the post-Super Bowl episode).

Both managed to edge out ABC’s Dancing With the Stars results show (20.9 million, 4.5) — in the demo, at least. Among total viewers, Dancing drew a slightly larger audience than American Idol, marking the first time a Dancing finale has outdrawn an Idol finale in viewers. In fact, in contrast to Idol, this is Dancing‘s most-watched season ever and its finale was up a whopping 15 percent from last year.

That left Tuesday’s most recent noisemaker, NBC’s The Voice (8.5 million, 3.8) squeaking to be heard at 10 p.m. The show fell 16 percent from last week to a new low. Biggest Loser (3.1) seems like it’s indeed ready for new coaches — the show is down 21 percent from last year for its lowest-rated finale ever.