Thanks for the suggestions, everyone. Also thanks to Gary, Linda, Mark and Matt for helping randomly select the draws. I'll first do the Girls 1st Round, before doing the males. Simply choose your FOUR favourites from each group:
Group A:
Kate Bush
Kylie Minogue
P!nk
Janis Joplin
Billie Holiday
Enya
Mariah Carey
Shakira
Group B:
Alanis Morissette
Annie Lennox
Grace Jones
Gloria Estefan
Aretha Franklin
Vera Lynn
Gladys Knight
Eva Cassidy
Group C:
Britney Spears
Celine Dion
Tina Turner
Susie Quattro
Gloria Gaynor
Marianne Faithfull
Alicia Keys
Nina Simone
Group 
Etta James
Dusty Springfield
Dolly Parton
Carly Simon
Tracy Chapman
Dionne Warwick
Joni Mitchell
Sonique
Group E:
Amy Winehouse
Madonna
Patsy Cline
Dido
Norah Jones
Dinah Washington
Janet Jackson
Nelly Furtado
Group F:
Whitney Houston
Tori Amos
Patti Smith
Tammy Wynette
Eartha Kitt
Chaka Khan
Mary J Blige
Christina Aguilera
Group G:
Sinead O'Connor
Beyoncé
Cher
Barbra Streisand
Lulu
Gabrielle
Sheryl Crow
Shania Twain
Group H:
Avril Lavigne
Diana Ross
Bette Midler
Björk
Melissa Etheridge
Sarah McLachlan
Donna Summer
Shirley Bassey