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Background

I'm trying to apply the sine-wave Tremolo effect to a few minutes of audio I have, and I'd like to set the Frequency (Hz) to be 0.25 to achieve 15 periods per minute. However, the UI of the Tremolo parameters popup seems to disregard anything more accurate than tenth of a Hz.

E.g. I can set it to 0.2 Hz to have 12 cycles/min, or 0.3 Hz to have 18 cycles/min, but manually entering 0.25 in the text-field besides seems to be ignored.

Question

Is there a way I can still achieve a 0.25 Hz Tremolo effect within Audacity somehow?

Or if not, is there some other free and/or open source software that runs on Linux or on the web that can do the trick? Command-line solutions also interest me if no GUI-based solutions are available.

Or if not, is there some proprietary and/or closed software to achieve this effect?

  • I tried it on v2.0.6 and it worked fine. Maybe there is another way to apply AM using Audacity, that will work on all versions. – Marc W Nov 17 '15 at 16:38
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According to a collaborator of the project this will be fixed when 2.1.2 is released.

Since that version is not yet released, and/or if you use an earlier version, the following is what I did to achieve what I wanted.

https://github.com/audacity/audacity/blob/ae5d29a04815cc41ccf36ef765a9f75636b8bd21/plug-ins/tremolo.ny#L22

(This file was installed at /usr/share/audacity/plug-ins/tremolo.ny on linux)

I've changed the above line to be

;control lfo "Frequency (Hz)" real "" 1 0 1

which made the slider more precise in the range 0..1

  • @n00dles Yeah, I agree my wording was more vague that I'd have liked, so I've edited my text somewhat. I hope you like it better this way as well. – Wizek Nov 17 '15 at 16:53
  • Cool, the real thing is definitely better! – Michael Hansen Buur Nov 17 '15 at 17:40
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  1. Change samplerate to the double

  2. Resample the file to half the length / one octave up (no timestretch / preserve tone magic enabled).

  3. Specify 0.5 Hz and apply effect.

  4. Resample one octave down again

  5. Change samplerate back to original

  • Nice tip! Thank you. So I've tried this on 1 min of audio with the "Change Tempo" effect: Changing the length to 30 seconds, applying Tremolo with 0.5 Hz, then changing length to 1 min, and it worked! However I am a bit worried. Since I "downsample"/"compress" to half the size (not sure if correct terms), don't I lose about half of the audio signal data in the process? Edit: If this effect could be achieved by "upsampling" to 2 minutes, then down back to 1, I would be less worried, but then I would need to set the Hz to 0.125, which is even more hopeless. – Wizek Nov 17 '15 at 15:32
  • Sorry, you're right.. I updated the post. See if that makes sense. You need to make sure the samplerate change doesn't affect tone. – Michael Hansen Buur Nov 17 '15 at 16:00

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