We’re guessing Slash never thought Sweet Child O’ Mine would look this rad.

We’re big fans of Smule’s nerd-tastic Ocarina app, which allows us to run around the office playing Legend of Zelda tunes, and then laughing about what big dorks we are. Smule’s latest musical app, Leaf Trombone: World Stage is half musical instrument and half game. If you just want to jam, as it were, Leaf Trombone offers a free play mode where you can work out your Dizzy Gillespe by either blowing into the iPhone’s mic, or tapping & dragging the screen to play notes. Plus and Minus keys let you jump up or down an octave, and adjustable sensitivity helps new players get used to the app’s controls.

You can also pick user-submitted tunes to play, Guitar Hero-style, as leaves fall to indicate where and when to hit the right notes. There’s even an online composer at the Smule website, where you can build your own tracks. We tested the app learning to play everything from the theme to The Office, to the main riff from Black Sabbath’s Iron Man.

Once you’ve worked on your leaf chops, it’s time to take your act on the road, via Leaf Trombone’s World Stage mode. You can either judge other users’ performances, or--if you’re brave--rock your favorite Leaf Trombone tune, and submit it for others to rate. It costs you three Leaf Tokens to unleash your musical genius on others, which you can earn by scoring others’ performances.

We had problems hearing audio a few times while judging, but what’s worse is that there’s no way to tell what song you’ll get stuck listening to. We spent half an hour racking up Leaf Tokens in order to be able to perform awesome tunes like 99 Luftballoons, Sweet Child O’ Mine, and the Mario Brothers theme on the World Stage, but we had to sit through several terrible renditions of Twinke, Twinkle, Little Star, and the supremely boring Auld Lang Syne in order to do it. It would be nice if there was some way to block certain songs, or only judge certain genres.