Aluminum wire is prohibited by code from any home or commercial wiring, so if you are buying at a reputable store you don't have to worry. You need not go to Monoprice to buy stranded 12 gauge.
As for the issue at hand, it is a basic law of physics wire cannot change pitch. However, coat it with snake oil and it can do anything. Of course, the price of snake oil varies. It's also extremely slippery.
As for the issue at hand, it is a basic law of physics wire cannot change pitch. However, coat it with snake oil and it can do anything. Of course, the price of snake oil varies. It's also extremely slippery.