Every great Apple product needs an app that shows off its unique features

Image: Apple Inc.

The 1984 Macintosh had MacPaint. The 2007 iPhone had visual voicemail and Google Maps. The iPhone 4 had FaceTime.

Steve Jobs offered two tent-pole demos last week when he introduced the iPad 2. iMovie was cool, but GarageBand for the iPad is Apple’s AAPL new must-have app.

According to a press release issued Thursday, the $4.99 program will be available for download before the end of the day. Meanwhile, the company has posted a slick guided tour here.

UPDATE: GarageBand for iPad and iMovie for iPad are now available for download.

It’s too soon to know whether real musicians will use the app to create great music. Or whether a generation of would-be musicians will use its “smart instruments” and avoid the hard work of learning how to play a real one.

But it does make a killer demo.

GarageBand runs on the original iPad, but it runs better on the iPad 2.

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[Follow Philip Elmer-DeWitt on Twitter @philiped]