Get ready, street musicians: Today Apple released its popular music-making app GarageBand for the iPhone. Now you can jam away on a set of onscreen drums, or strum a touch-based Smart Guitar, to compose musical masterpieces wherever you may be.

The slimmed-down iPhone app has all the features of the iPad app: a multi-touch interface with Smart Instruments (to piece together pre-assembled musical bits) and Touch Instruments (for those who want to play and record their own instrumental tracks). You can also record vocal tracks using the device’s built-in mic, and (with the help of an adapter) plug an electric guitar directly into your iDevice and record tunes through GarageBand’s amp and stompbox effects.

In total, GarageBand helps you knock out impromptu jam sessions, all without having to lug around a bunch of equipment.

Naturally, the iPhone version of GarageBand is shrunk down for a 3.5-inch screen.  My app experience on an iPhone 4 was smooth, without any force quits or stutters. And, not surprisingly, it was fun to tap away at the onscreen keyboard and drum set using only my thumbs. I made a complete (albeit heinous-sounding) song in a matter of minutes. So, if you’re looking for a solid music-making app to jot down song ideas or even create passable tunes while you’re wiling away time on your evening commute, GarageBand is the answer.

GarageBand was first launched as a Mac application, and later ported to the iPad with the launch of the iPad 2 in March 2011. “This is no toy,” Steve Jobs said of GarageBand on the iPad. “This is something you can use for real work.” Since then, a number of enterprising companies have released capacitive touch tools, such as guitar picks and drum sticks, that you can use with the app.

The iPhone version of Garage Band is, like the iPad counterpart, a big download. At over 501 MB, it took me at least five minutes over a Wi-Fi connection to complete the installation.

The app opens quickly, and operates only in landscape mode. Navigation is intuitive, and will be familiar to anyone who’s ever used similar music-making and recording software.

You select an instrument to play, adjust settings like reverb and echo if you’re not happy with the app’s defaults, and then tap away at a virtual instrument interface, hitting the record button if you’re ready to commit your work to, er, memory. Most of the instruments and tools look identical to their iPad counterparts, but there are a few small variations, such as in the piano, which has only eight keys instead of 15.

In the upper right-hand corner of the app, you’ll find an icon that lets you make adjustments to a single track, section or song. In the upper left-hand corner, you can click for a pop-over menu that will take you back to the songs or instruments panel, or let you swap between different forms of your current instrument (like for the piano, you can choose between options like Grand Piano, Smooth Clav, Classic Rock Organ, or Electric Piano).

Next to that there’s an icon that lets you switch from instrument view to song editing view. The editing view shows each of your recorded tracks so far, with opportunities to adjust, edit and loop sections.

Using Smart Instruments is a sure-fire way to create a song that doesn’t sound like it was hacked out by a team of rabid baboons. In this respect, GarageBand succeeds as a music-making device for people with no musical training whatsoever.

But what if you have musical experience — is GarageBand for iPhone a legitimate composition device? Not necessarily, as the app’s puny user interface is quite cramped. Still, this is an iPhone app, after all, and anyone using it to create music should be well aware that the premium music-making experience will be found on an iPad.

As with the iPad version, you can record and combine up to eight tracks, and then export to GarageBand or Logic Pro on the Mac for a bit more polishing. You can also share your iPhone-made masterpieces via iTunes or e-mail.

The app is a welcome addition to any mildly creative person’s iPhone or iPod touch. GarageBand is $5 and is now available for iPhone 3GS and up, 3rd and 4th gen iPod touches, and iPads.

Images: Ariel Zambelich/Wired