Unstable pitch when recording acoustic guitar

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Unstable pitch when recording acoustic guitar

Permanent link to this post Posted by Flamenco » Tue Dec 05, 2017 2:12 pm

I have successfully replaced a mic that didn't work properly with one that does - an inexpensive USB mic. The sound is clear but when playing back, the recording has seemingly random pitch wobbles, reminiscent of old cassette tapes. I have shut down all the other apps etc running but it makes no difference. I am using windows 10 - updated Dec 2017 on a Lenovo G50 laptop with plenty of disc space and audacity 2.2.0. I can't find other questions on this so is it a rare occurrence -and is there a cure?
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Re: Unstable pitch when recording acoustic guitar

Permanent link to this post Posted by DVDdoug » Tue Dec 05, 2017 6:29 pm

Try increasing your Latency/Buffer.

...The only thing I can think of is that you're getting buffer overflow so you're missing little random bits while recording and that's making it "skip" and intermittently play-back too fast.
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Re: Unstable pitch when recording acoustic guitar

Permanent link to this post Posted by Trebor » Tue Dec 05, 2017 8:09 pm

Try changing the Audacity project-rate from the default 44100Hz to 48000Hz , ( some recording devices will only work reliably if the Audacity project-rate matches their sample rate ).

Could also try increasing Audacity CPU priority form "normal" to "Above Normal" : that lowers the odds it will be interrupted by other processes running on the computer

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Re: Unstable pitch when recording acoustic guitar

Permanent link to this post Posted by Flamenco » Wed Dec 06, 2017 11:05 am

Thank you very much for your replies. I have applied both suggestions - changed the sample rate to 48000 and increased the buffer length from 100 to 200 ms.

I have recorded myself playing again and I still find little moments when the pitch wobbles. (It isn't my playing!) The artifact is in the recording as it can be heard at exactly the same moment again and again.

All other aspects of the recording seem fine - the sound is otherwise clear and precise but I am at a loss what to do with this noticeable wobble. Is there anything else I can try? (BTW - I rebooted the laptop this morning before starting the recording session).
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Re: Unstable pitch when recording acoustic guitar

Permanent link to this post Posted by Trebor » Wed Dec 06, 2017 12:56 pm

Flamenco wrote:I have recorded myself playing again and I still find little moments when the pitch wobbles. (It isn't my playing!) The artifact is in the recording as it can be heard at exactly the same moment again and again.

If you attach a sample WAV file with a wobble, 5-10 seconds, that could give us a clue as to the cause.

Here's instructions on how to attach audio file to a post ... viewtopic.php?f=49&t=64936
Attachments
generic acoustic guitar.wav
(801.01 KiB) Downloaded 6 times
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Re: Unstable pitch when recording acoustic guitar

Permanent link to this post Posted by Flamenco » Wed Dec 06, 2017 2:36 pm

Thank you.

Here is a WAV file of an example. The 'wobble' occurs at about 3.75 seconds.
Attachments
snip4.wav
(621.04 KiB) Downloaded 8 times
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Re: Unstable pitch when recording acoustic guitar

Permanent link to this post Posted by Trebor » Thu Dec 07, 2017 12:37 am

Flamenco wrote:Here is a WAV file of an example. The 'wobble' occurs at about 3.75 seconds.
snip4.wav (621.04 KiB)

I can hear the wobble & it's visible on the spectrogram ...

wobble.png
wobble.png (264.2 KiB) Viewed 217 times

But I've never heard Audacity produce a fault like that.
The only thing I can think of which could alter the pitch like that is Windows audio-driver software, (aka audio-driver).

You previously mentioned you had a USB webcam, that could be fighting your USB mic.
There is a setting on Windows recording devices to make a device the default recording device, that could resolve any conflict between recording devices ...
Image

There are alternatives to Audacity, e.g. OCENaudio , if the fault persists with other audio-editing software then it's a Windows problem.
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Re: Unstable pitch when recording acoustic guitar

Permanent link to this post Posted by kozikowski » Thu Dec 07, 2017 2:48 am

I have successfully replaced a mic that didn't work properly with one that does - an inexpensive USB mic.

Except this one doesn't work so well, either.

What was wrong with the original microphone?

The second longest post in forum history is by Bruno in Portugal. He wanted to record Flamenco guitar on his computer. That was the whole job. 18 forum chapters over three and a half months.

We got it to work, too, and well, but not with the original home-style microphone.

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Re: Unstable pitch when recording acoustic guitar

Permanent link to this post Posted by Flamenco » Thu Dec 07, 2017 8:12 am

Thanks, Trebor. I appreciate you taking the time with this. I will try the other software and see if that makes a difference.
The previous mic I was using was a webcam. The mic worked perfectly when I last recorded guitar - over a year ago with a laptop running Vista. My new Windows10 laptop didn’t like the webcam so I bought a new usb mic which installed itself in 2 seconds and which I used for the recording I posted. I removed the old webcam from recording devices and have disabled the only other one left (which is built in to the laptop) so I have one default mic which is my new one. Is there a way into a deeper level of the audio-driver software that could lead to a fix for this beyond the right click on the loudspeaker icon?

Thanks kozikowski - I will look for that thread and read through to see if it helps my situation.

I much appreciate the help.
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Re: Unstable pitch when recording acoustic guitar

Permanent link to this post Posted by kozikowski » Thu Dec 07, 2017 11:11 am

viewtopic.php?p=67836#p67836

I'm not sure reading Bruno's thread would help, but I know we went through a lot of sound quality issues with him. Simple recording tasks are not necessarily easy.

The current recordholder is Ian who was trying to present an audiobook from his apartment in Hollywood. That's the whole job. 39 forum chapters.

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