Differences between cable sound.

If you listen to Jazz and Classical i.e.,acoustic music,copper is best unless you REALLY have near-perfect system.
For rock doesn't matter much, loud and coarse anti-cable is more than enough.

There is some very interesting stuff here, not the least of which is the fact that Elizabeth and Schubert appear to be in agreement. After spending considerable time trying to wrap my head around that, I will make this comment. I have had good and bad silver and copper cables. I recently added a silver IC (VH audio Symmetry)and found that it did wonderful things--sweetened the top and significantly increased resolution without adding any brightness at all. It is an excellent IC! Appart from that, the rest of my cabling is Audio Magic Liquid Air. The LA's are also very good. This is a non metalic conductor which I think more people would do well to try. I think its character is a bit more like a very good copper than silver. Low grain, good dynamics, great bass slam. I think there is virtue in mixing cable types. It could be that adding silver to my existing Liquid Airs was just the right touch. I think both VH audio and Audio magic make great bang for the buck products. Not as cheap as blue jean, signal, etc, but they are very good.

for the record i find fusion audio romance gold interconnects superior to any silver or copper cable i have heard.

I think that your friend should try a few interconnects without any prior knowledge of their material used in their construction. The objective here for him is to find the best sounding interconnect that he can afford.

Knowing from which material the interconnect is constructed (copper, silver or gold) is purely for academic discussions and the ultimate purchase decision criteria should be strictly how the interconnect integrates well in your friend's system.

I've seen so many systems poorly matched from audiophiles putting a lot of money on their gear and putting not enough money on their cables. They have highly resolving electronics which sound is downgraded by the poor system matching interconnect/speaker cables.

Use your ears and go for the best sounding interconnects.

Many cable makers have excellent return policies or you can use the Cable Company's lending library. They also give excellent advice.