Sliding Stretch

Sliding Stretch allows you to make a continuous change to the tempo and/or pitch of a selection by choosing initial and/or final change values.

Tempo changes made without selecting a pitch change preserve the original pitch, and pitch changes made without selecting a tempo change preserve the original tempo. By changing only one of tempo and pitch and choosing the same initial and final value, you can use Sliding Stretch in the same way as Change Tempo or Change Pitch to produce a high quality fixed change. However Sliding Stretch lets you for example set the initial tempo change to -50% while also setting the final tempo change to +20%, the initial pitch change to +3 semitones and the final pitch change to +1 semitones.

Because of the high quality algorithm used, Sliding Stretch is normally slower compared to performing the same effect with Change Tempo or Change Pitch.

Note carefully that when you apply an effect to a time-stretched clip the changed speed of the clip will be automatically rendered. If you apply an effect to a selection within a time-stretched clip then Audacity will split the original clip so that the selection can be rendered as part of applying the effect.

If you apply this effect with an envelope present then there is a bug whereby the envelope is removed and the audio reverts to its full amplitude state prior to the effect being applied.

Accessed by: Effect > Pitch and Tempo > Sliding Stretch

Tempo Change

Initial and final tempo change values can be managed using the slider (which will move in whole number values only) or by entering a value in the box, which can be either a whole number or a number including a fraction.

Initial (%)

The percentage of the original rate required for the beginning of the processed audio. Positive percentages speed the audio up and negative percentages slow the audio down: -50% is half-speed, 0% is unchanged, 50% is 1.5 times the original speed, 100% is double speed and so on.

Final (%)

The percentage of the original rate required for the end of the processed audio.

Pitch Shift

The two "Initial" input boxes are interdependent. Entering the required value in one of the boxes for Initial Pitch Shift will automatically display the equivalent value in the other Initial box. Similarly, entering a value in either "Final" input box will display the equivalent value in the other Final box.

Initial (semitones)

Enter the pitch shift in semitones (half steps) required for the beginning of the processed audio.

Initial (%)

Alternatively, enter the pitch shift as a percentage of the original frequency as required for the beginning of the processed audio.

Final (semitones)

Enter the pitch shift in semitones (half steps) required for the end of the processed audio.

Final (%)

Alternatively, enter the pitch shift as a percentage of the original frequency as required for the end of the processed audio.

Time Tracks can be used to bend tempo more flexibly (also affecting pitch) using the Envelope Tool.

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