When ReBirth was released in 1997, there really was nothing quite like it. An application that emulates a rack full of classic Roland analog hardware (including two TB-303s, a TR-808, and a TR-909), this software put sounds that were once nearly impossible to find into the hands of an entire generation of musicians -- and put Propellerhead Software on the map in the process. Although official company support ceased in 2005, there is an active community of modders who make and trade songs and custom soundbanks, and the software is now freely available for Mac and PC users at Propellerhead's Rebirth Museum website.
The genius of the original ReBirth was that it not only emulated the sound of actual devices, it also reproduced the interface of the physical hardware it emulated. This accomplished two things: not only did it make it easy for users who were already accustomed to step sequencers on their drum machines and synths, but it put all of the controls right out there, somewhat simplifying things for people with no experience whatsoever. While this approach was pretty revelatory to folks on a standard Mac or PC, the "all out front" approach is somewhat intimidating on an iPhone!
Navigation on the app should be pretty intuitive for anyone who is used to multitouch gestures. While at the main screen you can double-tap on a device to zoom in, pinch to zoom in even further, or drag the screen around using two fingers. A task bar at the bottom of the screen (which can be toggled on or off by clicking on the Propellerheads logo) lets you: open, close, save, and delete song files; browse soundbanks (called mods); edit patterns; and upload your song to the ReBirth forums for sharing with others. To manipulate a sound or effect, just use your finger to punch a button or twist a knob.
While programming ReBirth devices can be complicated by all the zooming and scrolling you'll find yourself doing (hell, the desktop version was no picnic either), we think that you'll find that the sound of the software itself is every bit as good as that of the desktop version. Is it worth $6.99? Probably not for most people -- especially when you can get the original for free. Your best bet is probably to check out the ReBirth Museum, take the software for a spin, and then decide if you absolutely must have the mobile version. And when you do get rocking, drop us a line. We'd love to hear what you come up with!