[FFmpeg-user] Dropping 1 frame every n seconds

[Steve]

I would like to try and test changing the tempo of the audio in a video without losing sync and without having to blend or merge frames.

At 25fps, dropping 1 frame would allow the the audio to be pitched/time stretched by 4% and dropping 1 frame every 2 seconds would allow for 2%

I understand how to modify the audio with atempo but am not sure of the best method to drop one frame every second or every other second - is it possible with a standard filter command?