And now, instant gratification with a beat. Currently being test-marketed in a handful of cities is the newest advance in cineplex salesmanship: a vending machine that offers soundtracks. ”You know how you come out of a movie humming [its] music, and say, ‘I gotta get that soundtrack,’ but then you forget?” says Judy Jett, founder of Movie Music, Inc., maker of the machines. ”Well, this way you can’t forget.” Strategically located near theater doors, the units carry 360 CDs, each for about $16. Jett notes that some theaters sold out the Notting Hill and The Matrix CDs in 24 hours. For now, traditional outlets aren’t worried. ”We’re not unduly threatened by it,” says Tower Records spokeswoman Louise Solomon, who notes ”our average store sells at least 100 copies [of The Matrix] a week.” Meanwhile, Jett’s goal is to make the machines as common ”as fill-your-own-candy-bag stands.” That’s a sweet prospect for music fans.