Although not needed very often, knowing how to change the speed of your audio files can be important, especially if you are converting old reel to reel to CD or vinyl records to CD, and don’t have the native speed available to you when you initially transfer it. A good example would be trying to transfer and convert a 78 speed record, but your turntable only supports 33 1/3 speed. When the file is done transferring, everything will sound very slowed down and difficult to hear or understand.
Thankfully, there is a very easy fix for this problem by using a free to download program called Audacity. Audacity open-source and is for both Mac or PC and can be downloaded here: https://audacity.sourceforge.net/download/
Once you intall Audacity on your computer, the next step is to find the audio file you’d like to change. To do this, click file->open and locate it on your computer. When it’s loaded, it should look similar to the image below.
Now, to speed up the entire track, you need to select all by either pressing CTRL-A or by clicking edit->select->ALL. Once the entire track is selected, click effect->Change Speed.
A new dialogue box will show up asking for some input as to what speed to change. The nice thing about audacity is that it has preset options for LP records for converting 33 1/3 to 45 or 78 speed and vice versa. This makes it easy if transferring LP records and not knowing the exact percentage. Usually this is enough to get the appropriate speed for your recordings, however sometimes additional tweaks are needed, depending on the audio source.
Alternatively, you can apply the speed changes to sections of the audio by highlighting the portion you’d like to change with your mouse rather than selecting the entire recording.