Increase or Decrease Music Tempo without Pitch Change

FMOD Studio
1

Hello:

Is there anyway to increase or decrease the tempo of the music in an audio track without changing its pitch in the process?

Thanks.

2

You can counter the pitch change by using the FMOD Pitch Shifter DSP.

3

Awesome! Thank you so much!

4

I was having trouble getting the pitch of the Pitch shifter DSP plugin to shift accurately. I found an old thread that used a formula to calculate how much you need to shift for a specific keychange. Instead of providing the formula, i thought id just share my results from a google sheets doc. hope this helps some future person.

It would be awesome if the Pitch shifter plugin could just use a semitone or cents shifter rather than an arbitrary 0 to 2 number thing…

For now heres the numbers.
Imgur

1 Like
5

Very helpful, thank you for that!

6

Just dropping this info for anyone still reading. If you’re using C#/Unity, you can use the following functions to transform the values just as shown in the Pitch Shifter formula:

    private static float SpeedMultiplierToPitchSemitones(float speed)
    {
        return 12f * Mathf.Log(speed, 2f);
    }

    private static float PitchSemitonesToSpeedMultiplier(float pitch)
    {
        return Mathf.Pow(2f, pitch / 12f);
    }

The actual code I use is this:

    private void SetSpeed(float speed)
    {
        float pitch = SpeedMultiplierToPitchSemitones(speed);
        float pitchShift = 1f / speed;
        Debug.Log($"speed: {speed}, pitch: {pitch}, pitchShift: {pitchShift}");
        // change the tempo
        m_MusicInstance.setParameterByName("Pitch", pitch);
        // compensate for pitch change
        m_MusicInstance.setParameterByName("PitchShift", pitchShift);
    }

NOTE: This requires having parameters set up so that “Pitch” and “PitchShift” apply the same values to the respective controls.

1 Like
7

I’ve improved my code a bit. Here’s a glimpse:

    private void SetSpeed(float speedMultiplier)
    {
        float pitchSemitones = SpeedMultiplierToPitchSemitones(speedMultiplier);
        float pitchShift = 1f / speedMultiplier;
        Debug.Log($"speedMultiplier: {speedMultiplier}, pitchSemitones: {pitchSemitones}, pitchShift: {pitchShift}");
        // change the tempo
        m_MusicInstance.setPitch(speedMultiplier);
        // compensate for pitch change
        m_MusicInstance.setParameterByName("PitchShift", pitchShift);
    }

You can also rename speedMultiplier to pitch, which I have done in my actual code.

1 Like
8

This is very cool! Thank you so much for your help!