Sound Tweak Rpi4

[hestehandler]

This suggests to me the cache need not be very big if size confers no advantage.

I agree, from my observations with this, the larger memory just fills up with tracks that have already been played.  As long as the input buffer is bigger than the single largest file in a collection, it will be big enough.

That is not accurate. Logically the minimum size will be the sum of the size of the two largest tracks you have. While one track is playing from the cache, the next is being loaded into the cache.