Aluminum is especially resonant, light, and easy to work with.   Most big box hardware stores around here (Home Depot, Lowes, etc) have a section with steel and aluminum pipe and rod stock.    Check it out.  

cool.  i'd just been thinking about using pipe for a xylophone-ish instrument aqnd couldn't decide if it would work or not.  

Not that I am an expert on this at all, but it seems to me that aluminum would be too "soft" for something like this--especially if any real volume is desired.  Smacking chimes (tubular bells) with a rawhide mallet might be pretty devastating to aluminum.

Let us know how it turns out.