@darkfrank, let me suggest you try, only temporarily, bypassing the fuse of concern with a solid copper rod or a jumper wire soldered across the fuse. This will now be your reference, that is to say it can't be improved upon for purity. Once your ear/brain has heard this then try and find the fuse that gets closest to your 'reference'
This is what I did and selected a SR Blue but it was not long before I bypassed the fuse, not with a jumper wire across the fuse but by soldering a wire across the fuse terminals.
Let me be clear, I am not recommending this other than as an experiment.