Audio Crossfader

How the Audio Crossfader works

A crossfade is the transition DJs, radio stations and playlist apps use to move from one song to the next without a gap. Instead of the first track ending and the second starting, the two play at once for a few seconds: one fades out as the other fades in. This page does the same thing to files, so you can build a continuous mix, a workout playlist, a background track for a video or a slideshow, or a smooth join between two takes.

Crossfade length

The overlap is the number of seconds both tracks are heard together, and it is also the amount the total running time shrinks for each transition. Short overlaps of one or two seconds suit speech and podcast segments, where you only want to hide a cut. Five to eight seconds is typical for a party or workout mix. Ten seconds or more works for ambient music and long fades where tempos do not need to line up. The tool never lets a crossfade take up more than half of either track, so a short clip next to a long song still plays.

Choosing a curve

• Equal power keeps the perceived loudness steady through the transition. Each track follows a quarter sine wave, so at the halfway point both are at about 71 percent rather than 50. Use it for unrelated songs, which is most of the time.
• Linear fades each track in a straight line. With two different songs the middle of the fade dips by about 3 dB, which sounds like a small hole. It is the right choice when both files are almost identical, such as two takes of the same performance, because matching audio adds up in level rather than in power.
• S-curve starts and ends gently and moves quickly through the middle. Each song keeps its full level for longer before handing over, which suits DJ-style transitions.

Audio crossfader tips

• Trim first. Most songs have a few seconds of silence or a slow fade at each end. Remove it with the Audio Trimmer or Silence Trimmer so the overlap lands on music, not on quiet.
• Match the levels. If one track is much louder, the crossfade will lurch. Run each file through the Audio Normalizer first.
• Joining without overlap? The Audio Joiner puts files end to end with an optional gap of silence instead.
• Beat matching is not done here. For a seamless dance mix, tempos need to match; the Audio Speed Changer can bring two songs closer first.

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