How did Irish song meters differ from earlier bardic verse forms?

In the context of Irish literature, the transition from professional bardic verse to song meters marked a fundamental shift in both structure and accessibility.

Earlier bardic verse was characterized by highly complex, rigid rules of prosody and strict syllable-measured lines. These forms required extensive training—often spanning years—to master, as seen in the rigorous education of the filid (professional poets) who were required to learn hundreds of difficult meters.12

In contrast, the song meters that replaced them after the decline of the bardic order in the 17th century abandoned these syllable-based constraints in favor of lines defined by a fixed number of stresses. Key differences include:1

• Rhythmic Structure: Song meters moved away from syllable counting toward accentual patterns, utilizing lines with a set number of stresses.1
• Rhyme and Sound: While bardic verse relied on intricate, formal rhyming rules, the new song meters favored simpler vocalic assonance.1
• Language and Audience: The language of the new poetry shifted toward the vernacular of the common people, reflecting a move from aristocratic patronage to a more popular, accessible tradition.13