Copla de arte mayor sometimes called Octava de arte mayor or Copla de Juan de Mena is metric rather than syllabic which is a departure from most Spanish verse. I found an example poem at Vole Central and the form confirmed in an article by D C Clark in the Hispanic Review.

The Copla de arte mayor is:

1. stanzaic, written any number of octaves.
2. metric, amphibrachic tetrameter. uSu/uSu/uSu/uSu, the lines are often divided into 2 hemistiches.
3. rhymed, abbaacca or sometimes ababbccb.