I went digging.
APRA = Australasian Performing Right Association Limited
ECAD = Escritório Central de Arrecadação e Distribuição
SOCAN = Society of Composers, Authors and Music Publishers of Canada
VCPMC = Vietnam Center for Protection of Music Copyright
CS stands for collections society. In another age CS would stand for the Mafia.
These collection societies are actually the opposite of the mafia.
They collect royalties on behalf of the composers. If the composer has a publisher, the royalties are forwarded there instead (so the publisher can take their contractual cut).
They are the only way to protect your work if you are unsigned (think struggling artists).
AIUI there collection societies are collectives of publishers and look out for the people who own the publishing companies, they're not making sure the publishing companies act fairly and justly, they're making sure they sue people who are too small to defend themselves in order to boost the collections in order to support the publishing company owners.
CS stands for collections society. In another age CS would stand for the Mafia.
All but ECAD were found from here: https://www.cisac.org/