A very common ask. How can you change the tempo or the key of a CD track or any audio file (such as MP3 or wav). A common enough request – especially if you want to fit a track into another arrangement, or you want to practise along with a CD track or MP3. Why are they always so fast? Fortunately there is a very quick and easy answer whether you are on a PC, Mac or Linux. And it is FREE (but just a little bit fiddly.
A Step-By-Step Guide To Adjusting Pitch and Tempo
Audacity is a free to download cross platform recording software which is simple to use and perfect for working with digital audio. You can directly open MP3 files and CD tracks so you can start working on them straight away.
Let’s assume you are working with a CD, but you could just as easily do the same thing with an MP3 or *.wav or *.aiff file – or almost any kind of audio file.
Choose File > Open and navigate to the file or track on your CD then click on Open. The file will be converted into an Audacity project that you will be able to work on and then save. CD tracks automatically open up as 44.1 kHz stereo files. When you have done that, this is what you will see – and with a few more clicks you will have the recording at the tempo or pitch you want. Read on to find out how.
Once you have your file displaying as an audio waveform, you need to select the whole audio track.
Choose Edit > Select …. > All or click on the select tool, then click anywhere in the audio waveform and press Ctrl+A. You should see that the track is fully selected.
Once the audio track is selected, you can then access any of the following from the Effect Menu, as shown in the screenshot below.
Change The Tempo Without Affecting the Pitch
To change the tempo of an audio track without affecting the pitch in Audacity, go to Effect > Change Tempo. This option will allow you to speed up and slow down the audio track without changing the pitch. Notice there are several options to change the tempo: percent; bpm; or length. Very useful.
So when the Change Tempo dialog box pops up you can use the slider to change the tempo to a slower or faster speed. If you want to type in a specific number of seconds you’d like the audio to last you can type that in the “to” field underneath the slider. If your audio file as a specific number of beats per minute or BPM defined already, you can change the BPM instead. Experiment. There is a preview button. And if you go ahead and change the track then don’t like it, you can simply undo.
The good thing is Audacity will NOT destroy your original file, so you can experiment, and save the result as an Audacity project. Of course if you want to, you can export the result and over-write the original file if you wish. But far better to export to a newly named file, and keep the original intact.
Change the Pitch of an Audio Track without affecting Tempo
This is useful to experiment with if you want to change the key of an audio track, but leave the tempo unchanged.
Useful that you can experiment by either moving up or down the required number of semitones, or go for a percent change.
Change The Speed of an Audio Track
The final option in Audacity for adjusting the pitch and tempo is the ‘Change Speed’ option.
The thing with this option is it affects both the Tempo and the Pitch. It is unlikely you will want to do this if you are creating an audio track that you can play along to. It is more an effect you might want to use if you are doing a remix, or incorporating a sample into a project.
Saving the Result
When you have finished experimenting and are happy with your new track, there are several options for saving your work. If you choose File > Save Project As then you can save all your work in an Audacity project format which will have *.aup format. This is perfect if you just want to work within Audacity but you won’t be able to open your track in any other software.
If you want to create a standard audio file in full CD quality then choose File > Export….. then pick WAV from the drop down list next to the “Save as type”.
If you want to create an MP3 to the same as above but pick MP3 Files from the drop down list. Note that Audacity uses an external utility called the Lame MP3 Encode to export MP3 files. You will need to install this in advance. You can easily find out about the Lame Encoder and details of how to install it on the Audacity site.
The above, once you had done it a couple of times, will take you just a few minutes. Phew no more despair as you try and keep up with your favourite backing tracks while you are learning something new.
Adjust Tempo AND Remove Vocals
One of the reasons you might want to change either the tempo or the pitch of an audio track is so that you can play along with it. Sort of like a Karaoke. So you might want to combine the above with removing the vocals from your song track. I would recommend removing vocals first, then playing with the tempo and pitch as above.