There's an old but still mostly accurate MakeCD tutorial at
http://acdldp.emuunlim.com/bootablecdr.shtml. You'll need a copy of CD32.TM, which you can probably rip from the ISO image. (Hint: It follows the primary volume descriptior, starts with a series of asterisks (0x2a), is 2048 bytes in length, and probably begins at offset 34816.)
If your Windows or Mac software lets you create custom volume descriptors, you can use that, too. It's not the El Torito spec, though, so that won't work.
After burning the first track with MakeCD--presumably using track-at-once--you should be able to burn additional audio tracks, assuming the disc wasn't finalized.
Trev
