Online toolbox Aviary announced last week its new online music creator, Roc. Roc is free, in alpha, and available at http://aviary.com/blog/posts/online-music-creator.

When you first launch Roc, it’ll offer you the option to start off with an instrument (WHAT? NO COWBELL? — no, wait, I think they hid it in the drum kits) or to open a sample project. The sample project is the RocDemo which will give you a screen full of instruments.

This project is set in common time at 120 bpm. Each instrument has its own line, with a row of four dots per measure. If you want an instrument to play at one of the beats in the measure, click on the dot. There’s a bunch of instruments on the right side of the screen. You can add instruments individually or by the folder. I added a folder of drums and within a few minutes had several measures of percussion-y goodness playing in a loop, though sometimes the playing would skip — I think something wasn’t completely loaded. Individual controls on each instrument allow you to control panning and volume. If you have an Aviary account (free) you can save your creations, tag them, and set usage rights.

Just messing with this a little bit I found several things missing. I couldn’t find a way to change the BPM or time signature, for example. I couldn’t find a way to play tracks individually — it’s easy to play samples, but I couldn’t isolate an instrument on a track and just play it in a loop as a I added or subtracted beats. And I couldn’t find a way to record my own voice or cigar box guitar solo on top of the provided tracks.

Then I noticed that there was an “Unlock More Features” link at the top of the page, which I figured was a pitch (you’ll pardon the pun) for a pay version. It’s not; instead, it’ll unlock many of the features I missed if you’ll provide five e-mail addresses for beta invitations. Now, when I put up this post, it’ll go to over 15,000 people between the RSS feed and the e-mail and the Facebook “Like” page. But the thing is everyone receiving these posts has asked to receive them. I would be uncomfortable providing Aviary with five e-mail addresses unless I knew five people who are really looking for an online music creator – and, sadly, I don’t.

Roc will absolutely not take the place of more advanced desktop software any more than Phoenix can, for me, take the place of GIMP. But like Phoenix, sometimes you need accessibility and ease of use far more than you need every last little feature in your desktop software. Despite the fact that there are some fundamental things you can’t change about Roc (at least not without giving out some e-mail addresses) it’s easy to noodle around and crank out little musical loops. Play with it and see what you think.