With “American Idol” temporarily joining Fox’s Thursday schedule, 9 p.m. lead-out “Don’t Forget the Lyrics” is getting a major boost.

The competitive karaoke show averaged a series-best 5.2 adults 18-49 rating last night at 9 p.m., according to Nielsen overnights, getting a huge assist from “Idol’s” 9.1 lead-in.

In the same hour, ABC’s “Lost” slipped to a season-low 5.4, still winning the hour but down 5 percent from the previous week.

“Lyrics” actually finished first in the hour in total viewers with 14.6 million to “Lost’s” 12.8 million. Though the latter usually gets a good kick in digital video recorder viewership, it has seen its rating slide each week since its debut four weeks ago.

Of course it remains to be seen if “Lyrics” can carry over any of “Idol’s” bump once the smash reality singing show contracts back to two nights next month.

Fox was first for the night among viewers 18-49 with a 7.2 average overnight rating and an 18 share. CBS was second at 3.3/9, ABC third at 3.2/8, NBC fourth at 2.5/6, Univision fifth at 1.6/4 and CW sixth at 0.6/2.
 
At 8 p.m. Fox led with a 9.1 for “Idol,” followed by CBS with a 4.2 for “Survivor.” Univision was third with a 2.1 for “Al Diablo con los Guapos,” NBC fourth with a 1.8 for an hour of “The Office” repeats, ABC fifth with a 1.6 for a “Lost” rerun and CW sixth with a 0.7 for a repeat of “Smallville.”
 
ABC took the lead at 9 p.m. with a 5.4 for a new episode of “Lost,” while Fox slipped to second with a 5.2 for “Lyrics.” NBC was third with a season-low 3.1 for “Celebrity Apprentice,” CBS fourth with a 3.0 for a repeat of “CSI,” Univision fifth with a 1.6 for “Pasion” and CW sixth with a 0.9 for a repeat of “Reaper.”
 
At 10 p.m. ABC held onto the lead with a 2.7 for “Eli Stone,” with CBS a close second with a 2.6 for a repeat of “Without a Trace.” NBC was third with a 2.5 for “Lipstick Jungle” and Univision fourth with a 1.1 for “Amas de Casa Desperadas.”
 
Fox also finished first for the night among households with an 11.6 average overnight rating and an 18 share. CBS was second at 7.3/12, ABC third at 5.3/9, NBC fourth at 4.0/6, Univision fifth at 1.9/3 and CW sixth at 1.2/2.