Viewers in the 18-49 age group most-coveted by advertisers dropped by about 32 percent compared to last year's Idol," although the program was still the top show on U.S. television on Wednesday night.
The "American Idol" finale audience slumped to a record low, but the show's newly crowned champion Phillip Phillips hit No.1 on iTunes on Thursday with his first single Home.
Fox executives said earlier this month that the audience drop-off this season had been greater than anticipated and that several tweaks were in the works to freshen the format for 2013.
Despite the smallest TV audience since the show began in 2002, viewers cast a record 132 million votes for finalists Phillips and 16-year-old singer Jessica Sanchez.
And on Thursday, Phillips' first single, the folk-rock ballad "Home", topped the iTune charts, while his compilation album of "Idol" cover songs from Season 11 was in the No.3 spot.
Phillips, an acoustic guitar player and songwriter, said "Home" didn't represent his style of music, which he described as more jazz and rock.
It's not really something I would write," the 21 year-old from Georgia told reporters on a conference call.
It's a little too pop for me. I don't really put in the ohs and oohs. I am a little more rock than that," he said, adding that he was excited to get his own album out.
They are probably better singers than I am, but I play the guitar a lot different ... I feel like I am different," he said.
Fox said "American Idol" had held onto its spot as the most-watched show on U.S. television for the 2011-12 season just ended in total viewers, 18-49 year-olds and teens.
The talent contest helped Fox to its eighth straight season victory among 18-49 year-olds, outperforming CBS by 7 percent, third-place NBC by 28 percent and ABC by 33 percent.