On April 7, rock singer-songwriter David Cook performed a medley of hits in honor of the late Rock and Roll Hall of Famer David Bowie at this year's American Idol season finale, with four other talented musicians and past winners.

An all-star tribute for David Bowie

Cook was joined by fellow Idol winners Kris Allen (Season 8), Lee DeWyze (Season 9), Nick Fradiani (Season 14) and Phillip Phillips (Season 11 winner). The medley of Bowie songs that they performed included "Starman," "Rebel Rebel," as well as "The Jean Genie," and they all accompanied themselves on acoustic guitars.

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It was followed by an impromptu performance of William Hung (who was best known from the third season of the reality competition) and his version of Ricky Martin's "She Bangs."

Cook served as mentor for the Season 15 finalists

Previously in this season, Cook served as a mentor for this year's contestants, and he collaborated with two of the finalists on two different duets.

These collaborations included a rendition of Collective Soul's signature song "The World I Know," which he sang with contestant C.J. Johnson, and his own song "Light On," which he preformed a duet with power-vocalist Olivia Rox. On the day following his Idol mentoring, Cook performed his latest radio single, "Heartbeat," on the Top 4 results show this season, which was well-received and it fared well on the Billboard Hot 100 charts.

Season 15 finale had an array of talent from Idol alums

Aside from Cook, other guest performances on the season 15 finale included country mega-star Carrie Underwood, Season 3 winner Fantastia, Season 5 winner Taylor Hicks, Season 6 winner Jordin Sparks, as well as Academy Award winner Jennifer Hudson, among many others. It also included cameos from its past judges Randy Jackson, Paula Abdul and critical judge Simon Cowell.

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Earlier in the season, on the Top 5 results show, Grammy-nominated pop singer and Idol alum Adam Lambert performed "Mad World" and a duet of his new song "Welcome to the Show" with singer-songwriter Laleh.