Miley Cyrus had to scrap plans to perform at the memorial service for one of her favourite contestants on The Voice on Monday (18Mar19), because she was so overcome with emotion.

The Wrecking Ball singer had to ask her dad, Billy Ray Cyrus, to perform Amazing Grace at the Celebration of Life for Janice Freeman, telling mourners she was too upset to sing alone.

Instead, she joined the chorus at Mariners Church in Irvine, California and sang along with her father.

Before the song, Miley sobbed through a heartfelt tribute to 33-year-old Freeman, who died from a blood clot in her lungs, telling fellow attendees, "I was never her coach, ever. She was always mine.

"I've learned more from her than anyone that I've ever gotten the honour to be in the room with, not just vocally. I should've gotten more lessons than I did, but she taught me everything that I know about love."

Miley explained she had planned on singing for Janice, but then added, "Just losing her is just too much for me, so... my dad's gonna take care of this for me."

Breaking down onstage, Cyrus, who served as Freeman's coach on the 13th season of The Voice, added, "I'll always be your sister, I'm here for you, and I'm here for your family, and Janice I'll miss you more than I could ever say."

Following her friend's death on 2 March (19), Miley penned an emotional note, revealing she had been left heartbroken by the sudden tragedy.

Taking to her Instagram account, she insisted Janice was the "best f**king singer in the world".

"I miss you so much it hurts. Everywhere... but so did you," the pop star wrote, referring to Janice's previous health battles with lupus, cervical cancer and meningitis. "(Janice hurt) so often. So much pain and no one would ever notice because of the smile and joy you constantly radiated. I am trying my best today to celebrate your existence but I can’t help but just deeply mourn over your absence...

"You are my world. I will never forget you or stop loving you. I am forever yours."