A system for preparing data, operable with a server computer system having a store for a first file comprising data (e.g. audio data) and a plurality of sets of lossy data generated from the data in the first file. The system comprises a requesting component for requesting at least two sets of the plurality of sets of lossy data; a receiving component for receiving the at least two sets; and a combining component for combining the at least two sets in order to generate a second file. The data in the second file is of reduced lossiness with respect to the data in the first file.