Just try it!
Go to VLC settings:
Advanced / disable timestreth
To save it between song picks and app restarts:
Audio / save playback speed.
Both of these should be visible on the speed slider box.
Try different slower speeds, it will take constant changing of the speed to get it just right for each song, and I hope this can be simplified with speed presets for each song. If anyone is interested in adding features or improving functionality, share your ideas.
Here are my thoughts to improve this:
Add the two settings above, onto the slider box. Also add a new feature save speed for current song
Range is too large to be practical, reduce and have simple default of 60 - 110% and customizable.
Dragging slider moves after a large change, not useful at all, ans in fact it makes it not possible to simply drag to a nearby speed
Custom arrow changes, down to 0.001%
Smooth speed transitions
Lines for indicating all %, 5 and 10 bold lines. Makes it obvious how much to move to reach a certain speed.
Make playlist based on saved speeds, which would be selectable between the preset you want. So if you set four speeds for a song that you enjoy, and order it descending, slowest last, you could have four different playlists with the same songs, but four different overall speeds.
It will take a while to code all that but I think it would be worth the effort instead of constantly re-adjusting speed.
Once desired default speed is set for all songs, (will also takw a while) you could use regular playback speed, but instead of it being labeled 99% and 101% it would be -1% or +1%.