Donna Summer's Funeral -- Packed with Music Legends

Donna Summer's funeral is underway right now in Tennessee -- and TMZ has learned, several legends in the music biz are present ... including famed producer David Foster.

In addition to producing several tracks for Donna Summer -- Foster has worked with practically every other singer on the planet ... including Michael Jackson, The Bee Gees, Mariah Carey, Beyonce, Prince, Madonna ... the list goes on.

Sources tell us, Italian record producer Giorgio Moroder is also present at the funeral. Moroder produced several disco hits with Summer, including "Love to Love You Baby" and "I Feel Love."

We're told Donna's casket is covered in white roses. The singer's entire family is also at the ceremony.

As we reported yesterday, the private invitation-only ceremony is taking place in Nashville -- and roughly 1,000 people are attending.

Donna passed away in Florida last week after battling lung cancer. She was 63.