How to Mesh Tempos With Audacityby Chris Anzalone ; Updated September 22, 2017
Audacity is a an audio recording program designed for the home musician on a budget. With this software, you can not only record original music, but also edit it to perfection. Among its myriad features, Audacity allows you to mesh different audio files together to create one multi-layered file. In order to do this properly, you will often need to adjust the "tempo," or speed of your audio files, so the music contained within each file lines up properly.
Open Audacity, which you can find under your "Start" menu -- under All Programs. If using the Mac OS X version, open your "Macintosh HD" folder and then "Applications" to find Audacity.
Click "File," "Import" and "Audio" on your menu bar and use the navigation window to select your first song file. Make your selection and the song file will appear on your Audacity window as a long horizontal bar with wavy lines. This is your first "track," or layer.
Click "File," "Import" and "Audio" again to select your second song file. Your second file will appear directly beneath the first, also resembling a horizontal bar with wavy lines. At this point, if you press "Play" on you Audacity window, the two songs will overlap with each other, but if they do not have the same tempo (speed), they will sound out of sync.
Click either one of your audio tracks -- in the left column -- to highlight it. Choose the track containing the file that you want to edit. For example, if you have a melody track and a vocal track and you want to speed up the vocals to conform to the melody, you would select the vocal track with your mouse.
Click "Effects" at the top of your screen. When the drop-down menu appears, click "Change Speed." A new window will appear on your screen.
Drag the "Percent Change" slider to the right, if you want to speed up your selected file. Drag it to the left if you want to slow down your selected file. Move the slider only slightly, and then press "Play" to hear the difference. Continue making small, gradual shifts to the speed until your selected file plays at the same speed as the other file. Click "OK" on the Change Speed window when you finish.