Toroids are useful cores when minimal magnetic flux leakage and significant amounts of power are design parameters. That said, an E-I stack of laminations is MUCH easier to wind primary and secondary windings. With a toroid core you generally need to wind all the wire on a shuttle first and then pass the shuttle as many times through the core as there are turns on the winding. With small gauge wire and hundreds of turns this can be a real PITA. Of course toroids can be wound by hand without a shuttle if you know how long a length of wire is required for each winding, but except for a few dozen turns this is also a PITA.
Another approach, used in variable auto-transformers for example, is to wind a long strip of flat steel through the toroid windings. The steel is coated with varnish or shellac to minimize eddy currents in the core. This is not something I would attempt to do unless I was able to salvage the core strip from a discarded transformer. Finding a source for the grain-oriented silicon steel strip could be difficult for a one-off project. This stuff usually comes from a specialty mill in large rolls delivered on a flat-bed truck and requiring a fork-lift to move around. Slitting to the required width adds to the cost.
There are companies that specialize in custom transformer fabrication to your specifications, including toroid transformers. Their services aren't cheap, but if I knew exactly what I wanted, that is where I would go to first for a quotation before attempting to wind my own.
Why are you considering the use of a toroid audio transformer? What are you trying to do?