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I need a program (with an easy learning curve) that lets me slow down mp3 (at the very least this format) music and audiobook files. The software needs to be able to slow down the audio at the chosen speeds without altering the pitch and accuracy of the words being pronounced. Perhaps like the language software "Byki Deluxe's" "SlowSound" feature? I'm learning a foreign language (German) and I find the speeds at which the books are being read too fast. I need to hear the pronunciation of each word much more clearly to learn how to pronounce the words myself.

Is there such a product out there? Now, I know you can slow down stuff in VLC but it sounds really artificial. I need something that slows down audio files without altering the accuracy of the words being pronounced.

It doesn't have to be freeware; ease of use and quality is more important to me.

Win 7 64-bit. IE 8.

Edit: Are there any software-for-pay like Audacity? Only the beta works in Win 7. Also, I'd prefer to be able to slow down a file live and not have to create a new file to use the feature.

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    What do you mean "without altering the accuracy of the words being pronounced?" Just because you slow down something does not mean you can magically increase the bitrate...
    – soandos
    Feb 6, 2012 at 19:51
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    Have you looked at audacity? Feb 6, 2012 at 19:51
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    Sorry, I'm not sure how to put it into words. Not increasing the bitrate but that the slowed-down word should keep the pitch of the word intact. Like if the program was spitting out the word "apple" in a slowed-down state, it would be like app-ple and not a "blur" such as ahhh-puull.
    – verve
    Feb 6, 2012 at 20:02
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    @soandos You don't need to increase the bitrate. The technique he wants software to do is called 'time stretching'. It's possible. Feb 6, 2012 at 20:21
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    The suggestion for Audacity is one that would do it. However, any software that is used for audio editing will probably have some implementation of it. I produce electronic music, and my software that I use can do it using various methods, however, it would be overkill and difficult for you to figure out quickly (per your requirements), and it's also pretty expensive. But if you don't like Audacity, knowing the name of the technique should give you something to go on when Googling. Feb 6, 2012 at 20:50

7 Answers 7

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As Raystafarian notes, audacity has a feature called Change Tempo which promises to change the tempo of the recording without adjusting the pitch. I assume this is the effect you're looking for.
Please note that (as soandos noted in the comments) this does in no way generate a more detailed recording. The recorded information is constant, this just changes how it is played back (and, thus, can make a recording sound slower).

For further reading, there's also the Wikipedia article on Audio timescale-pitch modification.

If you don't like audacity, this feature isn't exclusive to that application. There are even Winamp plugins that can do this. I'm pretty sure there are several more options.

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    I can confirm that I have used this feature in Audacity. I am definitely not an audiophile, but it did exactly what I expected it to.
    – EBGreen
    Feb 6, 2012 at 20:03
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    @verve From the audacity website: "It is a mature Beta, intended to become the new 2.0 stable version in the near future. Most users should download the Beta." - I think the beta will do fine. Feb 6, 2012 at 20:08
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    @verve I don't know what you expect. What you request can be accomplished in a 3 step process: load, process, export. Then you have a new file that you would use the same as the old one. If you want to change the tempo live, look for a plugin for your favorite audio player. Feb 6, 2012 at 20:22
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    @verve I don't know if it is required, I assumed it would be the most practical. Feb 6, 2012 at 20:40
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    You could always play the processed audio within Audacity without saving, but it would have to be processed again the next time.
    – Bob
    Apr 15, 2012 at 10:07
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For a purpose-built program to do exactly that, check Express Scribe Transcription Software from NCH Software. The free version handles MP3 and other formats. The first feature on the feature list is "Variable speed playback (constant pitch)". My daughter uses it for her translation and transcription business. Very simple user interface, because it's not intended for all the things that Audacity & GoldWave are designed to do.

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  • Hmmm...finally tried it. When I slow down the speed of a voice in an audiobook the words sound warble-like. Not good...
    – verve
    Apr 15, 2012 at 8:59
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    Sorry to hear that. I haven't used the program in a couple years, but it used to be pretty decent. Is there anything else running that could be taking CPU cycles and causing the warble effect? I'll check with my daughter, too.
    – yosh m
    Apr 16, 2012 at 14:07
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    Well, I've got a quadcore and 8GB of RAM...it warbles less than Audacity though. Ask your daughter if it distorts at the lowest speed?
    – verve
    Apr 18, 2012 at 8:53
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    She said the last time she used it was a year ago - and she does not recall having any problems. Have you tried writing NCH support? Is it possible that some other program is accessing the sound card? Or that something is stealing CPU cycles? You could try killing all the background tasks to see if the problem goes away.
    – yosh m
    Apr 23, 2012 at 17:29
  • Hmm...let me take a looksy. Is she using a new product to transcribe?
    – verve
    Apr 24, 2012 at 23:08
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GoldWave also has the feature of slowing without pitch change, and allows for much manuel control of the process, more control than needed most times. the item is called "Time Warp" found in the effects menu.

It also will do batching of layers of filtering and manipulations of the sound, so you could do a bunch of sound files the same way. it works in windows 7 without a single crash ever, but I am using the older 32bit version (5.06).

It has instant realtime previewing of filters, so it could be used to listen slower, without changing anything, like all realtime changes it requires cpu speed.

it is not free, only free to try. It has all the complicated stuff in it , but they didnt try and create psudo simplicity?, so I find it is easier to use than other software.

many of the "pro" video programs now have the features of slowing the video and slowing the audio without pitch change, if it was a video that your trying to slow down. They are far from free :-)

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    Let me take a look. Would Goldwave work on Amazon's Audible audiobooks?
    – verve
    Feb 6, 2012 at 20:46
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    probably not, it only uses the standard formats, and codecs. wav , mp3 , pcm, raw, flac, ogg, I think it only even does Mp3 writes because of codecs installed on the machine already. it isnt a player or capable of messing with any DRM, it is more an authors tool. In formats it would be very limited. for me it is like the virtual dub for audio.
    – Psycogeek
    Feb 6, 2012 at 20:56
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Sony Digital Voice Editor has the feature you're looking for. It is free and flawless.

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Use Corel VideoStudio, any version you have access to. This software is largely for working on video files but also has some features to slow down audio files.

I've already worked with this software for slowing down movies to learn languages.

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Try using Winamp and the "Pacemaker" (http://www.surina.net/pacemaker/download.html) plugin. You can change the "tempo" and this will help stretch the time without any distortion. Superb!

Note: Since Winamp is not currently downloadable from it's own website (due to change in ownership from AOL to radionomy), you can download it from http://winampplugins.co.uk/Winamp/ for now.

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Windows comes with an app that does this already: Windows Media Player. Just start playing your audio, and then right click inside the player. Select Enhancements --> Play speed settings.

Menus - Enhancements -- Play Speed Settings

You will see a popup, which will let you slow down or speed up your media:

Speed Change Popup

Move the slider to the left to slow down play speed. Move the slider to the right to speed up play speed. This is all done in real-time, so no new files are created.

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