Hobart, that cable is advertised for use with 12v landscaping lights and also outdoor speakers, but any two conductor power cable also has to be suitable for use with 220v lines that have a voltage peak a little over 300. Audio amplifiers, which typically have a power supply section maximum voltage around 40, are no problem.
Also, all commercial copper wire is better than 99.9% pure, so don't worry about either oxygen or whatnot. It's often not understood that a speaker wire simply serves as a guide rail for the electromagnetic wave traveling along its outside. The energy that penetrates into the wire and latches onto the electrons for guiding is lost as heat and doesn't directly contribute to the sound. There's no possible way for using "lighting wire" to be harmful to the sound(or any other wire to be more helpful).
