The major problem with Al wire is that the ends connected to the various boxes/outlets etc. corrode over time. Al corrosion/oxidation is not conductive whereas copper's is. That is why the house fires (in very new housing at the time too) occured and Al wiring was ultimately banned in many jurisdictions.
Aluminum wiring
I recently moved into a house with aluminum wiring and am considering converting over to copper. Is there a benefit to converting for sound quality?