ffmpeg – How to play a loop of a video with slower speed without changing the audio pitch?

I am trying to learn guitar. I have some videos I’d like to study and play along. I am looking for the command line argument that does the following:

• Play part of the video, from timestamp 1 to timestamp 2.
• Loop playback of that part,
• Adjust the speed without changing pitch (I can play along at a slower speed).
• Pipe that to a video player like FFplay or VLC.

I am currently using VLC to achieve this, but VLC can only slow down the audio/video within certain limits, 0.5x 0.67x e.g.

I want it to be a custom percentage so I can increase speed from 0.50 to 0.55 then 0.60 etc.

I studied the FFmpeg and FFplay documentation, but that is quite overwhelming.