Choose two songs to mash up. Attempt to select songs in the same key or with similar chord progressions.
Convert your chosen songs to WAV or MP3 format if in another format. Audacity fails to recognize songs in WMA or AAC format. Rip songs on an audio CD to your computer in WAV format, if necessary.
Open Audacity to import your first song into the program. Select "File," "Import" and "Audio" from the menu bar, then select the audio file of the song. Your song appears in Audacity as a waveform because it is a stereo track. Add the second song by selecting "File," "Import" and "Audio" from the menu bar. The songs appear in two separate tracks.
Adjust the pitch to your second song to the match the pitch of the first song. Highlight the entire track by selecting the left panel of the track. Click on "Effect" from the menu bar, then "Pitch" and "Tempo" followed by "Change Pitch." If you understand how to determine pitch, you can simply select the appropriate key. If you do not understand, you must find the pitch through trial and error by adjusting the keys.
Highlight the track for the second song again to change the tempo of the second song to match the first song. Click "Effect," "Pitch" and "Tempo." If you know the beats per minute of the first song, you can adjust the tempo to the appropriate number. If you do know it, you must find the tempo through trial and error.
Sample the desired vocals in the second song that want to join with the first song. You can alternate the vocals in both songs. Mute the track to only hear the vocals by selecting "Solo" in the left panel of the track. Highlight the part of the vocals you want to sample by clicking the selection tool and copying and pasting it into first track where you desire the sample to begin. Continue the process throughout the song.
Click the area with the pasted vocals in the first track and hit the space bar to listen to the combined vocals. Clean up the sound quality of the blended vocals by removing extra instrumentation. Select the part of vocals needing a cleanup. Click "Edit" and then "Split Delete." Repeat this process when necessary.