Two British rock stars paid tribute to the late singer George Michael with song.

Elton John teared up while paying tribute to his friend George Michael during a concert in Las Vegas on Wednesday.

With a picture of Michael lighting up the backdrop of the stage, he performed “Don’t Let the Sun Go Down on Me.” The 53-year-old Michael died on Christmas Day. John called his death one of the “saddest moments” of his career. He said he knew Michael from the start of WHAM! and the two collaborated on music.

John also tweeted a photo of the two, writing: “I am in deep shock. I have lost a beloved friend – the kindest, most generous soul and a brilliant artist.” He said Michael donated to causes without fanfare.

Watch John’s performance here.

Meanwhile, Coldplay frontman Chris Martin has paid tribute to fellow British singer George Michael during a visit to a London homeless shelter.

A video posted on Facebook by the Crisis homeless shelter shows Martin strumming “Last Christmas” on guitar and singing with one of the shelter’s residents. The 1984 song was a hit for Michael’s former band Wham! and has become a holiday classic.

The homeless have been on Martin’s mind this holiday season. Last week, he performed in New York at a benefit for a homeless shelter there.

Police say an initial autopsy has been “inconclusive” and more tests must be done to establish a cause of death.