Pure Silver Wire

Silver is a better conductor which is important when conduction is the only issue.  Now I don't recommend using a poor conductor for interconnects and speaker cables, but conduction (opposite of resistance) isn't the only concern in audio.

Silver is 7% better conductor than copper, so by making the cross section 7% bigger you get the same current carryng capability with copper.

I recently tried some very high quality silver plated copper 8 awg speaker cables, expecting them to be awesome.  they were very harsh...now many people don't realize what harsh it--harsh is when the upper frequencies are much louder than the lows and mids.  So those nice heavy speaker cables are destined to become a nice heavy power cord.

As others have mentioned, silver is often reported to be harsh in analog cables (note this does not apply to digital cables since digital signals are 1s and 0s so lows and highs are transmitted equally.  I highly recommend silver in digital cables). 

Different grain structures of copper seem to give the best performance.  

Jerry

Remember brightness or harshness varies a lot from person to person.  Be tweeters are harsh to some.

One reason this could vary is hearing loss.  As an old guy, my upper frequencies are weak so if something seems harsh to me, all I have to do is take my hearing aids out and voila, no harshness. 

but music sounds much better with my hifi hearing aids in, so I prefer to avoid enhanced upper frequencies and listen with them in.

Jerry

@richardbrand while what you say is correct, it doesn't cause silver to preferentially transit one frequency over another.