Joseph Parry (PHH 18) composed MERTHYR TIDFIL (also called DIES IRAE), first published in Llyfr Tonau Cynulleidfaol Cenedlaethol Cymru (The Welsh National Book of Congregational Tunes), a collection of hymn tunes Parry compiled and published in several parts from 1887 to 1892. The tune is named after the town of Parry's birth and means "the martyr Tydfil." The similarities of lines 1, 2, and 4 find a fitting contrast and climax in line 3. The harmonization invites part singing, but the music must not be taken too slowly.

--Psalter Hymnal Handbook