Changing pitch in an iOS audio player—like Alvin and the Chipmunks

I found this code fragment in StackOverflow. I think this is what I want to use. But I cannot get it to change the pitch—as I expected it to. I figured changing the 44100.0 up/down would affect the pitch. But I'm getting no change, regardless of the setValue.

NSMutableDictionary *settings = [[NSMutableArray alloc] init];    
[settings setValue: [NSNumber numberWithFloat:44100.0] forKey:AVSampleRate];

Cl开发者_运维技巧early I'm missing something.

Any additional fragments available to give this some more context?

Quoting answers from the related question.

There is a Time-Pitch Stretch Tutorial on the DSP Dimensions site.

and...

Take a look at Dirac. It’s free of charge, though not free software.