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'[EE]: A musical question'
2004\07\07@233305 by David VanHorn

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Ok, This has to pass for "oddball question of the year".

I've been asked if there's any (reasonably simple) way, to lock an incoming audio tone, to standard musical notes.   If I understand this right, the effect would be something like Cher's "Believe" vocal track.  This was done with heavy post processing, and is out of the ballpark here.

Alternatively, any reasonable way to let a performer know when they are reasonably close to a standard pitch, and by that I mean probably five octaves of notes, with sharps and flats.

I don't mind telling you kids, this one makes my head hurt.

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2004\07\08@035658 by hael Rigby-Jones

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>-----Original Message-----
>From: David VanHorn [spam_OUTdvanhornTakeThisOuTspamCEDAR.NET]
>Sent: 08 July 2004 04:33
>To: .....PICLISTKILLspamspam@spam@MITVMA.MIT.EDU
>Subject: [EE]: A musical question
>
>
>Ok, This has to pass for "oddball question of the year".
>
>I've been asked if there's any (reasonably simple) way, to
>lock an incoming audio tone, to standard musical notes.   If I
>understand this right, the effect would be something like
>Cher's "Believe" vocal track.  This was done with heavy post
>processing, and is out of the ballpark here.

The effect was produced by a vocoder IIRC.  You can get software solutuions
for PC's, but proffesional software that works in real time tend to be quite
expensive e.g. http://www.nativeinstruments.de/index.php?vokator_us is 289
Euros.

However, a quick google threw up http://www.vocoder-plugins.com/ which
appears to be a free solution for DirectX.

Regards

Mike

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2004\07\08@052330 by Per Linne

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And I've read (in a statement by the producer I_I_RC) that they used a Clavia Nord Modular. :-)
http://www.clavia.se/nordmodular/index.htm

PerL


{Original Message removed}

2004\07\08@110955 by M. Adam Davis

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The reason why this is so difficult is that a human voice contains more
than the one tone you are after.  You not only have to shift the main
tone - you have to shift all the harmonics and sub tones that are
present in the voice.

Solving a simplified problem is not terribly difficult:
Assume the input is a pure sine wave
Measure the frequency of the sinewave
Find the closest 'good' frequency
Output the 'good' frequency

In the analog realm this can be done by converting the frequency to a
voltage, putting it through a series of comparators which output
specific voltages that are then converted back to a frequency.

So the simplified voice problem:
Find the dominant frequency (FFT --> most powerful sine)
Find closest match to a good frequency and get the difference
Shift all the frequencies found by this same difference

I suspect that vocal processors find the difference and then speed up or
slow down the audio samples (filling in with dynamically gathered
samples or throwing out a cycle here and there) so the orginal voice is
completely preserved (ie, no need to generate 100's of sine waves)

So the simplified difficult voice problem could be:
Find dominant frequency
Find difference between dominant frequency and the ideal frequency
Assuming a fixed input sample rate, slow down or speed up the output
sample rate to bring difference to 0
When the output becomes more than one cycle behind, throw away one cycle
of input data
When the output is about to overrun the input buffer, copy the previous
cycle of input and insert into the buffer

I've only dealt with a little voice generation (no real processing)
before, so the models I understand are simplified.  I doubt that even
the last method will output professional quality sound, but it would be
fun to make and experiment with.  I can see a DSPic performing this work
- the hardest part is the FFT and controlling the output DAC speed
accurately enough.

PC based software would be more difficult because the input and output
sample rates are fairly fixed.  Software would have to resample the
sound which brings its own problems.

If it were really this simple, though, every karaoke machine would
include it.

If you pursue this, keep us informed!

-Adam

David VanHorn wrote:

{Quote hidden}

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2004\07\08@121548 by M. Adam Davis

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Also do a search on PIC Guitar Tuner.  You'll find an atmel version, and
you may find the original PIC version.  It does part of what you want.
I think EPE or another magazine made a tuner with a PIC as well, so you
should find one somewhere fairly easily.

-Adam

David VanHorn wrote:

{Quote hidden}

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2004\07\08@162151 by Ken Pergola

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Hi David,

I realize you are probably going to build something yourself but...just for
kicks...

Check out the company called Eventide (http://www.eventide.com) if you have not
heard of them. They have been around for ages (over 30 years) and are famous
for their Eventide Harmonizers.

There are other companies that make pitch correction/pitch shifting
electronic equipment (just a sample below):

DigiTech Vocalist VR ~$340.00 (http://www.digitech.com)
TC Helicon VoiceWorks Vocal Processor ~$700.00 (http://www.tchelicon.com)

Have fun Dave!

Best regards,

Ken Pergola

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2004\07\08@174545 by David VanHorn

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At 04:21 PM 7/8/2004 -0400, Ken Pergola wrote:

>Hi David,
>
>I realize you are probably going to build something yourself but...just for
>kicks...
>
>Check out the company called Eventide (http://www.eventide.com) if you have not
>heard of them. They have been around for ages (over 30 years) and are famous
>for their Eventide Harmonizers.

Thanks.  I know them from way back.
We had an Eventide Digital Delay, which someone had edited to:

Even_I__ Dig__a_ __lay

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