"From 6 September, all religious ceremonies can proceed with 50% of venue capacity, regardless of immunity status of attendees."
This is subject to appropriate protective measures including social distancing between groups, use of face coverings, etc.
See www.gov.ie/en/publication/73a24-public-health-measures-that-will-come-into-place-in-september for this and other information regarding the loosening of coronavirus restrictions.
From 20 September choirs and music groups may reconvene (see page 17 of the government booklet 'Reframing the Challenge' below for details, and also the HSE guidance on religious worship from June 2021).
The government's latest strategy plan for Covid-19 is Reframing the Challenge: Continuing our Recovery and Reconnecting.
Restrictions on religious services will be removed from 22 October 2021.