Martin 4100 Extended Life SP Phosphor Bronze Acoustic Guitar Strings Lightstar rating 5Bob RexSeptember 14, 2011To me these strings are both bright and warm, but I think warm wins out. These are not as bright as Elixers or the D'Addario EXP (coated) strings, or many others on the market. By the same token they're not as warm as the John Pearse strings that were originally shipped on my Guild GF-50 NT from the Westerly, RI factory in 1990. To me they're middle of the road goodness, and I'd love nothing more than a lifetime supply of these, thank you. Hmmm, now if I could only get an endorsement deal.