Forever For Now - Octave Shifter (Mac/Universal/Free)

From the homepage:

"With the success I had with my previous Audio Unit, the Reverse Sampler, I set out to create another one. This time I wanted to do a realtime pitch shifting effect with a range of plus or minus one whole octave. Initially I thought it would be the easiest to make an effect that could only shift exactly an octave up or down.

I tried several variations to create a decent pitch shifting algorithm but I couldn't get anything to sound anywhere near a decent quality pitch shifter. I clearly recalled the availability of pitch shifting algorithms on the Internet and I set out to use one of the existing algorithms as a base for my Audio Unit.

Having found several comparable algorithms and implementations I decided to stick with the pitch shifting code available on Stephan M. Bernsee's DSP Dimension website. In record time I had implemented his code in my Audio Unit and I though it was ready for release, but I was wrong.
Help from above

While testing my Audio Unit I found out it would distort stereo input signals and would also generate a lot of static when the effect was placed in an effect chain multiple times. I contacted Stephan himself to ask what was causing my problems.

After mailing back and forth with almost instant replies from Stephan each time, he had modified the code so that it properly separated computation for each of the input channels, solving all problems. With the improvements made to the effect I polished the code and recompiled the Audio Unit."

Octave Shifter Audio Unit features

The audio unit provides the following features:

* Realtime pitch shifting from -1200 to +1200 cents
* Works on any amount of input and output channels at any sample rate
* Adjustable FFT size ranging from 512 to 8192 and dynamic oversampling
* Industry standard Cocoa user interface and compliance
* Freeware

It's a Universal Binary so it will run equally well on both Intel and PowerPC Macs. You do need Mac OS X 10.4 (Tiger) or higher to use this software.