What is the role of Mathematica in WolframTones?
It’s the language and system in which WolframTones was developed, and it’s what’s used to run this site. (Specifically, the site is powered by webMathematica running on a collection of servers. Searches are done using gridMathematica.) Many symbolic language and pattern-matching capabilities of Mathematica are used for WolframTones. As well, of course, as its optimized CellularAutomaton function, and music and graphics Export function.