Lips

For this you need to score in any 20 songs of the Party Classics disc, you need to play the Full song not short. Also to make sure this unlocks correctly play all the songs in Solo mode.
Scoring can mean just getting 10 points, just as long as you score something and finish the song.

Here is a list of all the tracks you'll need to play:
“Addicted To Love” by Robert Palmer
“American Pie” by Don McLean
“Black Velvet” by Alannah Myles
“Brass in Pocket” by The Pretenders
“Doctor Jones” by Aqua
“Every Rose Has Its Thorn” by Poison
“Friday I'm in Love” by The Cure
“Groove Is In The Heart” by Deee-Lite
“I Think We’re Alone Now” by Tiffany
“I Touch Myself” by Divinyls
“I Want to Know What Love Is” by Foreigner
“I Will Survive” by Gloria Gaynor
“I'm Too Sexy” by Right Said Fred
“Is This Love” by Whitesnake
“It's Not Unusual” by Tom Jones
“Kiss Me” by Sixpence None The Richer
“Laid” by James
“Let’s Get It Started” by Black Eyed Peas
“Live is Life” by Opus
“Love Shack” by The B-52’s
“My Sharona” by The Knack
“Red Red Wine” by UB40
“Rehab” by Amy Winehouse
“Rhythm of the Night” by DeBarge
“Rock and Roll All Nite” by KISS
“She Will Be Loved” by Maroon 5
“Shiny Happy People” by R.E.M
“Son of a Preacher Man” by Dusty Springfield
“Sweet Home Alabama” by Lyrnyrd Skynyrd
“These Boots Are Made For Walking” by Nancy Sinatra
“To Be With You” by Mr. Big
“True Faith” by New Order
“Tubthumping” by Chumbawamba
“Unchained Melody” by The Righteous Brothers
“Wannabe” by The Spice Girls
“What’s Up” by 4 Non Blondes
“When a Man Loves a Woman” by Percy Sledge
“Word Up” by Cameo
“Y.M.C.A.” by Village People
“You're Beautiful” by James Blunt