How Do I Slow Down an MP3 File With Audacity?

By Shea Laverty

Using Audacity's effects menu, you can slow the tempo of an MP3 to turn an upbeat song into something a little more relaxed -- or pitch the singer down so you have Darth Vader on lead vocals. You can change the tempo and pitch independently of one another for more tightly focused effects control, or together for uniform tempo and pitch slow-down. Each of these effects have their own tool: "Change Tempo," "Change Pitch" -- and "Change Speed" for both pitch and tempo.

Tempo Only

Step 1

Select the section of the MP3 file you want to slow down. If you're changing the tempo for the whole file, you can skip this step.

Step 2

Click "Effect" and select "Change Tempo."

Step 3

Drag the slider in the Change Tempo dialog to the desired percentage. You can also change the percentage using the Percent Change text field, or change the beats per minute or length using the provided fields.

Step 4

Click "Preview" to test out how your slow-down effect will sound. Adjust the tempo change as necessary and click "OK" when you're satisfied with the result.

Pitch Only

Step 1

Click "Effect" and select "Change Pitch."

Step 2

Drag the slider in the Change Pitch dialog to the desired percentage. You can also change the percentage using the Percent Change text field, or change the pitch using the drop-down menus and semitones text field. Editing the ranges in the frequency text fields will also change the pitch.

Step 3

Click "Preview" to test the pitched-down clip. Adjust the pitch as necessary and click "OK" when finished.

Pitch and Tempo

Step 1

Click "Effect" and select "Change Speed."

Step 2

Drag the slider in the Change Speed dialog to the desired percentage. You can also change the percentage using the Percent Change text field, or use the drop-down menus to select an original speed and the lower speed, based on the standard revolutions per minute of a vinyl record.

Step 3

Click "Preview" to test the sped-down track and adjust the speed as necessary. Click "OK" when you're finished fine-tuning the clip.

Tips & Warnings

  • After you've finished editing your clip, you can save it as an Audacity project file by selecting "Save Project" or "Save Project As" from the File menu. You can also save it directly as a new MP3 file or overwrite the original file by selecting "Export" from the File menu.
  • To export to MP3, you need to download and install the LAME MP3 encoder. Without it, you'll have to save your file in another format.
  • Changing a clips pitch or tempo can result in minor quality loss, as the clip must be re-sampled. Repeated re-sampling from changing the same clip segment repeatedly can result in a poor quality clip. Use the "Undo" option from the Edit menu, or the Ctrl-Z keyboard shortcut, rather than manual pitch editing to undo erroneous or undesired changes.