Audio and tempo matching

Matching imported audio to the song tempo

Audio files created by the Export or Bounce functions in Reason include information about their original tempo. When you import such an audio file, it will automatically be stretched to fit the tempo in the new song.

However, if you have imported audio which has a steady, but unknown, tempo, you can adjust the imported clip to the song tempo. You can either use the Clip Tempo Scaling function to manually “stretch” the audio clip as described in “Tempo scaling Clips”.

Another way is to disable the automatic stretch for the audio clip and then adjust the sequencer tempo to match the clip. This is done in two steps: first you adjust the song tempo to the imported audio clip without Stretch enabled and then adjust the song tempo back to original - with Stretch enabled on the audio clip:

1.	Select the clip containing the imported audio file and choose “Disable Stretch” from the Edit menu or context menu.

Disabling Stretch makes the audio recording in the clip play back at the same tempo regardless of song tempo in the sequencer.

Disabling Stretch on a clip containing an imported audio recording.

2.	Start the sequencer and adjust the sequencer Tempo, up or down, to match the tempo of the audio recording in the clip.

If necessary, enable the metronome click in the sequencer to get an audible tempo reference. Continue adjusting the tempo of the song until it matches the tempo of the audio recording.

3.	Adjust the length of the clip so that it plays the entire audio file (or as much as you want).

4.	Select the clip and select "Bounce > Bounce Clip to New Recording" from the Edit menu or context menu.

The new recording will sound the same, but include information about the tempo you set in step 2.

5.	With the audio clip still selected, choose “Enable Stretch” from the Edit menu or context menu.

6.	Adjust the song tempo back to the original BPM.

As you adjust the song tempo, the tempo of the audio recording will follow along accordingly - without affecting the original pitch of the recording. This is done by stretching the audio. Reason does this automatically in two parallel steps: a real-time “preview” stretch so that you can instantly hear the result of your tempo changes, then a high quality stretch “in the background” to further improve the sonic results. As soon as high quality stretch is in progress, the “Calc” indicator on the Transport Panel shows a progress meter:

The CALC progress meter appears when Reason performs high quality stretching of audio.

Since the high quality stretch is performed in the background, you can still continue to work with your song without any interruption. When the high quality stretch data has been calculated, the Calc indicator goes out and the high quality audio data will be heard on playback.