Sinwave volume modulation of a track

[Rick_123]

Hi,
how do I take a track and then change its volume/amplitude using a sinewave of 0.2Hz)?
So that, let’s say instad of music I have a fixed frequency, you hear always the same pitch but the volume would constantly change up and down following a sinewave form?
I definitely did this ages ago in Audacity, but don’t remember how or if I used some plugin.
Thank you
Rick

[Trebor]

Audacity comes with a tremolo effect, it’s in “Distortion & Modulation” sub menu.