That Leaf Trombone app Smule demoed at the last iPhone Event is now available. It actually looks pretty decent.

Leaf Trombone World Stage includes new, never-seen-before iPhone features, such as:

Self tutorial — a music box accompanies users as leaves softly float toward the correct notes, enabling users to learn the song, simply by following the leaves on the screen and moving the Leaf Trombone up and down; similar in concept to Guitar Hero

Judging capabilities — Anyone can perform a tune on the Leaf Trombone before a global audience

Once a player has submitted a song to the World Stage, self-appointed judges, randomly selected from anywhere in the world, providing an instant critique of the performance, using a combination of emoticons and text

Judges can rate each performance using a 1-10 scale. The evaluation is then added to player's standings and the player's rank is updated

Sophisticated browser-based composition tool provides unlimited new music

A new interactive learning tool enabling anyone to compose and create music for the Leaf Trombone

This is from the same people who made the Ocarina app, in case you were wondering about its pedigree. Some more demo videos here, here and here. Just don't load them all at the same time like I did, and pass out from the cacophony. [App Store]

Listening Test: It's music tech week at Gizmodo.