NEW YORK – Adam Lambert showed his softer side on "American Idol," earning a standing ovation for his smooth performance of "The Tracks of My Tears."

Guest mentor Smokey Robinson, who originally performed the classic song with the Miracles, rose to his feet after watching the 26-year-old theater actor hit all the right notes during Wednesday's Motown-themed installment of the "Fox" singing competition.

Lambert, who's from Los Angeles, ditched his rocker duds for a sleek silver suit and smoothed his black hair back into an Elvis-style pompadour.

Judge Simon Cowell said Lambert delivered the night's best performance and became a star in his eyes. Fellow judge Kara Dioguardi agreed, saying Lambert showed "true artistry."

The four judges were also equally impressed by the vocal stylings of Allison Iraheta, Matt Giraud and Kris Allen. Cowell liked Allen's cover of "How Sweet It Is" but said the 23-year-old married heartthrob from Conway, Ark., needs to show more swagger and confidence.

Lil Rounds and Danny Gokey scored mixed reviews for their respective renditions of "Heat Wave" and "Get Ready." Cowell told Rounds, 24, of Memphis, Tenn., she'd missed a potential "Idol"-defining "moment" by picking the wrong song (he'd rather hear the soul singer belt "I Heard It Through The Grapevine"). But the cranky judge had harsher words for Gokey, deeming the 28-year-old crowd pleaser "clumsy and amateurish."

Michael Sarver and Megan Joy had a tougher time on stage. Judges slammed Sarver's cover of "Ain't Too Proud To Beg." Even sugary-sweet Paula Abdul chimed in, comparing the 27-year-old oil rig worker from Jasper, Texas, to an old-school Vegas lounge act.

Joy, 23, of Sandy, Utah, was targeted for her shaky take on "For Once in My Life." Cowell called Joy's performance "horrible" while Randy Jackson declared it a "train wreck" and "mad crazy."

One of the 10 finalists will be sent packing on Thursday's elimination show — unless judges act on the new rule that allows them to save a favorite contestant they feel has been unfairly booted by voting viewers.