Semitone-based Frequency Shifter for live-use? Building one?

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samtastic
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Semitone-based Frequency Shifter for live-use? Building one?

Post by samtastic » Sun Jul 17, 2011 2:58 pm

hi all,

I'm working on a live set that consists of six sub-group channels of audio (these are the result of bounced audio parts, live synthesis and a few midi/drum rack combos).


I'm looking for an audio effect similar to the Frequency Shifter device, but one that works in semitone-steps rather than Hertz (as Frequency Shifter does). One that is semitone-based and can be mapped to a pot... I'd like to be able to shift things up & down as far +-12 (an octave) as well as steps in between.


I know that the transpose knob for audio clips does this. But as I said, I'm working with subgroups, and some of these contain outboard synthesis and drum racks.



It's late here (and I'm about to go to bed). but can anyone think of a way that the standard Frequency Shifter device could be racked-up and built into such a device... or is there a M4L Device around that does what I want?



Kind regards,
Sam

bigbadotis
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Re: Semitone-based Frequency Shifter for live-use? Building one?

Post by bigbadotis » Sun Jul 17, 2011 5:47 pm

Frequency shifters don't preserve relationships between harmonics but rather change every frequency component by the same amount.

As an example, if you have a waveform with a fundamental freq of 440 Hz and a single overtone at 880Hz and shift by 440 Hz you get 880Hz and 1320Hz which is no longer an octave relationship.

You need to do pitch shifting by speeding up / slowing down playback, granular methods, or using a phase vocoder.

samtastic
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Re: Semitone-based Frequency Shifter for live-use? Building one?

Post by samtastic » Mon Jul 18, 2011 1:11 am

bigbadotis wrote:Frequency shifters don't preserve relationships between harmonics but rather change every frequency component by the same amount.

As an example, if you have a waveform with a fundamental freq of 440 Hz and a single overtone at 880Hz and shift by 440 Hz you get 880Hz and 1320Hz which is no longer an octave relationship.

You need to do pitch shifting by speeding up / slowing down playback, granular methods, or using a phase vocoder.


Cheers : )

I'm not overly-familiar with the Freq Shifter effect (I've not got a lot of amazing sounds from it, only subtle changes). But you you saved me some time messing around with it this morning (so thank you).


Can anyone think of any standard Ableton audio effects that could be used for this purpose? I'd rather stick with Ableton effects than use a third-party effect (as I'm getting towards the finished end of a live-set, and I don't want to potentially sacrifice stability for this effect!)


time to strap on my thinking cap : )

Again, thanks for the food-for-thought

oddstep
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Re: Semitone-based Frequency Shifter for live-use? Building one?

Post by oddstep » Mon Jul 18, 2011 7:47 am

Grain delay. 0 feedback. 100 wet signal. Set repeat rate to minimum milliseconds setting. Adjust other parameters untill it works for you.

chapelier fou
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Re: Semitone-based Frequency Shifter for live-use? Building one?

Post by chapelier fou » Mon Jul 18, 2011 8:30 am

For audio clips, you can map them to a keyboard range
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samtastic
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Re: Semitone-based Frequency Shifter for live-use? Building one?

Post by samtastic » Tue Jul 19, 2011 1:35 am

chapelier fou wrote:For audio clips, you can map them to a keyboard range
yeah and I could just map the transpose pot, but I'm working with audio clips, midi clips and audio from outboard effects/synths...



cheers Oddstep. Will give it a shot!

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