For example, upon distribution, the ISWC is used by Performing Rights Organisations (PROs), such as SOCAN, to identify the musical work and the rights holders. Without the ISWC, the PROs will not be able to uniquely identify the musical work, which leads to delays in royalty payments. Moreover, a musical work is only eligible to receive an ISWC when all participants have an IPI, hence the importance as an author and/or composer to join a PRO in order to obtain its IPI.
The ISWC is an optional metadata for most DSPs. Why is it optional? Obtaining an ISWC can take up to six (6) weeks and the declaration of the musical work can only be done if all (100%) rights holders are identified with their unique IPI. In addition, not all PROs issue an ISWC to an original musical work (proof of performance must sometimes be provided).
What do collecting societies do when an ISWC is missing? They try to identify the rights holders using matching techniques using other identifiers provided such as the ISRC and they work in collaboration with technology companies such as BMAT, which have a database of music and metadata augmented by all the players in the music industry.