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Need to play back 1/2 speed.
Rusty Horizon
post Nov 17 2006, 18:26
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I have some old open reel tapes that were recorded at 1 7/8 ips, but the slowest my machine supports is 3 3/4 ips. Most software I've found retains the pitch of the music when slowing down, but I need to change the pitch with the speed. Has anyone used software that works for this application? (I'm running an XP PC, but have some access to a MacBook, OS 10.4)
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post Nov 17 2006, 19:29
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Errrrm... the easy thing is do both things. The difficult thing is keep the pitch when changing speed, but this is interesting in (audio) mixing software, so it's mostly used there.

I'll give you an example to do it with audacity ( any program that works with samples should be able to do it)

1) Open your wav
2) double click to the waveform so that audacity selects it all
3) menu "effect", "change speed"
4) enter -50 as the value.
5) you're done.

[Edit : audacity : http://audacity.sourceforge.net/ ]

This post has been edited by [JAZ]: Nov 17 2006, 19:31
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post Nov 17 2006, 22:23
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Just to add options here...this is really easy to do with either of two Sony products: Sound Forge 8 or ACID Pro 6.

Assuming you've already got your file at double speed, here's how you'd do it in Sound Forge:
  1. Open the file in Sound Forge
  2. From the menu select "Effects > Pitch > Shift..."
  3. Make sure "Preserve duration" is UNCHECKED.
  4. With the "Semitones to shift pitch by" slider, move it to the left until it indicates a shift by -12 semitones.
  5. Click OK.
  6. Save the file and you're done.
In ACID there are a few more steps, but still not too complicated.
  1. Start with a new, empty project.
  2. Using either Windows Explorer or the built-in explorer in ACID, find your double-speed file.
  3. Drag and drop the file into the track area in ACID.
  4. The "Beatmapper" dialog will pop up...just click Cancel.
  5. Right click on the clip and select "Clip Properties".
  6. Verify that the ACID type is set to "One Shot".
  7. In the "Pitch shift (semitones)" box enter "-12".
  8. Close the Clip Properties box.
  9. From the File menu, select "Render As..." and choose the file name and type you want.
  10. Click Save and your new file will be saved.
There are fully functional trial versions of both packages on the Sony Media Software Site. (I think that you'll need to license an encoder from Sony to save files as MP3 format...it's been so long since I licensed my software I can't recall...)


This post has been edited by Patrick: Nov 17 2006, 22:25
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post Nov 18 2006, 02:26
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And just to let you know, playing back at 3 3/4 and then halving the speed does not give exactly the same frequency response as playing at 1 7/8, but it may not be so bad that you notice.
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Rusty Horizon
post Nov 19 2006, 17:36
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Thank you all! I used the Audacity recommended by [JAZ] and it worked great. Pat's suggestion looks like it would work great also, but I'm a big fan of freeware. And also pdq has a very valid point if your trying to do anything hi-fi, but my source is mostly speach, do cutting my frequency response to 10kHz would most likely just cut out some tape hiss. Thanks again!
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