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What I think I need to do is create some code that lets me read in a bunch of raw sound files (ie a complete sound font for say a guitar), processes these files (to construct chords), and outputs the result as another set of files.

My question: can anyone point me to some code that does something close to this task, that would save me from having to do everything from scratch?

EDIT: answer below have suggested I use garage band which I have had a look at. it looks like a great tool. I can construct my 24 chords on garage band. but then I need to save it as MIDI, and write my own code to process this midi file, adjusting the volumes of individual notes, save it, then feed it back through garage band recording the sound. Can anyone point me to some code that would get me started processing midi thus?

Sam

PS if it is of any interest, this is what I am working on:

http://imagebin.org/125562

The difficulty I face is how to voice the chords... if I just do {C4 E4 G4} for the C major chord, and {G4 B5 D5} for G, etc, it is going to sound horrible

A pianist simply doesn't move from C to G like that. There is an art to voicing, so that each note attempts to move a minimal distance to its new resolution.

And I can't see any formula for depicting this in a way that is key agnostic.

So I am attempting instead to play all Cs Es and Gs, to create a sound texture for 'C major'

If I put all of the respective amplitudes under a bell curve, each major or minor chord should have its energy centred around the same point, so the effect would be that the texture changes without giving any overt / crude impression of moving up / down

Does this make some sense now? The task becomes: how to construct 24 textures?

P i
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  • I'm not sure why you need to adjust the volume of the individual notes. You can do this in Garage Band. – Nathan S. Dec 02 '10 at 00:10
  • You want each note to move the minimal distance to the new resolution, so as a brute force approach you could just check all chords and use the one that moves each note the minimum distance from the last chord played. (Of course, you can be smart and not try everything, but even the brute force search is probably fast enough.) – Nathan S. Dec 02 '10 at 00:12

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If you are still looking for a solution, iOS5 (finally!) includes the Core Audio MusicPlayer. - it can read/write midi files, load soundfonts, play back midi with a variety of option.

Mac MusicPlayer Developer Reference

iOS MusicPlayer Developer Reference

stormCloud
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spring
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You could create all the chords in Garage Band and then export the sounds from there to be used in your app. (Although your app will be larger with all the digitized audio.)

Nathan S.
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  • Great suggestion! I have just been playing with it. I can see that using copy and paste it would only take me 10 minutes to get my 24 textures. But I would need to process the midi file to weight the volumes on individual tones. – P i Dec 01 '10 at 05:55
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You could probably peruse Stephan Bernsee's example code that comes with his free Dirac LE time stretching library. It has two classes, EAFRead and EAFWrite that read/convert/write audio files. You can get it from http://dirac.dspdimension.com. Check out the mobile/iOS folder that comes with the library. You can simply replace the call to his library with anything you want (like sample rate conversion to transpose sound, check out http://www.musicdsp.com for hints/code that does this).

tahome
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