The word ‘transcription’ simply implies a transfer of music written for one instrument to another, without specification. Mozart’s piano sonatas, for example, originated not only from the sound world of the piano but also from a particular conception of sound that goes beyond one particular instrument. Mozart often adapted his operatic style to his piano works, and in so doing crossed the borders of what was considered possible for the instrument. His and Bach’s styles of composing provide a clear argument in favour of the idea that the majority of works composed for piano cannot be considered purely as piano music. The reverse, however, is also true for transcriptions for the piano. Given that Wagner composed at the piano, any transcription of his operatic works must of necessity bear a close relationship to the original.