In the Republic of Ireland music publishing performance royalties are collected by a performance rights organisation (PRO) called Irish Music Rights Organisation (or commonly shortened as IMRO).
In other words you can think of Irish Music Rights Organisation (IMRO) as an equivalent to ASCAP, BMI or SESAC that you would find in the United States.
The Irish Music Rights Organisation collects performance royalties for songwriters and music publishing companies because performance royalties have the writer’s share and the publisher’s share.
The writer’s share is the part of a music publishing copyright that goes to the songwriters from obvious reasons which is quite frankly writing the song (e.g lyrics). This money is generated when the song is used on Radio, TV, Live Concerts and online interactive or non-streaming services.
So in order for an artist or a band to receive their writer’s share of performance royalties in Ireland it is in their best interest to register with IMRO as a songwriter (i.e writer membership).
On the hand the publisher’s share can be split where the artist get’s 50% of the publisher’s share given that the artist has a co-publishing agreement with a music publishing company. This publisher’s share in the context of “performance royalties” is the income which comes from sources similar to the writer’s shares.