The girl group recently announced plans to stage Viva Forever! in London later this year, which features hits from their back catalogue.
"It's quite special to know that your music is a part of a musical," Mel B told MTV News.
"That's what we've always dreamed of, and it's actually happening from one conversation three, four years ago to actually being in a theatre in December, which isn't far away. It's quite amazing."
Asked which songs have made the production, Mel B teased: "I can't really tell you which songs are in it, because I think that's part of the surprise, but I think our songs tell a beautiful story that has nothing to do with the Spice Girls.
"It's the essence of friendship and honesty and love, and the actual storyline is beautiful. I don't want to spoil it for everyone; if you want to be entertained, if you want to be surprised, you just got to go and see it."
Viva Forever! will open to the general public on November 27 at the Piccadilly Theatre in London.
Watch the Viva Forever! promotional video below: