4. The method as in claim 1 wherein the first audio data is stored within the first audio file in a plurality of fixed-size access units and wherein generating the universal representation comprises packing the fixed-size access units into a plurality of fixed-size audio data structures, the fixed-size audio data structures of the universal representation being larger than or equal to the fixed-size access units of the first audio file.
6. The method as in claim 4 wherein the bookkeeping data is packed into the fixed-size audio data structures of the universal representation along with the fixed-size access units.