Multiple instances of the same recording in the same release

A Release can contain the same sound recording multiple times

Typical examples include Boxed Sets where a record company publishes both "original" albums and "best of" compilations together. In such cases the same Recording can be in one Release more than once. Two cases need to be differentiated:

1. The two (or more) recordings are truly the same and they even use the same binary sound recording file. In that case one SoundRecording composite should be used for both uses of the recording – unless there are metadata differences that need to be preserved (e.g. a change in the band name); and

2. The two (or more) recordings are truly the same but two (or more) different audio files exist. In that case two SoundRecording composites must be used even if all the metadata is the same. The only differences between the two SoundRecording are the ResourceReference and the TechnicalResourceDetails.

Receivers of ERN messages therefore need to consider that they might receive an ERN message containing two (or more) SoundRecording composites with the same identifier and that two (or more) TechnicalResourceDetails point to the same resource file.

If no binaries are to be communicated, the distinction between the two cases disappears and case (1) is the appropriate approach.

PS: There is actually a third case where the two (or more) recordings are of the same song (i.e. Musical Work) – but they are distinct recordings. Examples include a studio version and a live version of the same song. In that case the two recordings would be identified by different ResourceIds and two SoundRecording composites will need to be used. However, this case is different as these are different recordings.