Most people will know this band from their great track on the “Eisteddfød” compilation from the same label. After this Omne Datum Optimum did the splits with Gae Bolg and Nothvs Filivs Mortis. “Missa XXI” was anounced as “very bombastic” and made with contribution with Gae Bolg. Indeed, the singing will sound familiar to Gae Bolg fans, but the music is by far not as bombastic as that band. ODO has much Gregorian singing, medievalish music and drumming, but less bombastic.