Launch your preferred digital audio workstation such as Pro Tools, Cubase or Logic.
Import the audio files you have selected for your song mash.
Trim off the silences. The method for doing this varies slightly according to which program you use. Find the trim tool in the “Tools” menu or access a button on the main control bar, denoted by a scissor icon. Click to the left of the first peak in the audio sound wave to trim the silence at the start.
Drag both files left, as far as they’ll go so the first note in each is at "zero."
Play both tracks at the same time. Click the “S” icon on each track intermittently. The “S” stands for solo. By soloing the track, you mute the other audio, enabling you to determine which of the two tracks is the fastest.
Determine the tempo of the faster track. Access the “Tools” menu and select either “Analyze” or “Beat Calculator,” depending on the your program. The digital audio workstation measures the peaks in the audio file energy pattern to determine the tempo.
Click on the slower of the two tracks to highlight it. This assigns subsequent edits only to that track, rather than both.
Alter the tempo. Digital audio workstations have a function for stretching or squashing the audio to increase its speed without increasing its pitch. For example, in Audacity this tool is called “Tempo Change.” In Pro Tools it is called “Beat Detective.” In the box marked “Tempo,” type in the tempo in beats per minutes, of the other track.
Trim out the sections that you want to remove, using the trim tool. While one song is prominent, the other is muted and then they switch. Create the muted sections by trimming out the audio and deleting it. The trims in each song must correspond so that there are no gaps. For example, if you trim zero to 10 seconds from the first song, don’t trim it from the second.
Drag song No. 2 on top of song No. 1. If you’ve trimmed correctly, the gaps should enable the tracks to sit together.
Highlight the joins between the section and select the “Cross Fade” or “X-Fade” tool. This smooths out any clicks or glitches caused by editing two pieces of audio into one.