Wikipedia
Bertsolaritza or bertsolarism is the art of singing extemporary composed songs in Basque according to various melodies and rhyming patterns. Bertsos can be composed at a variety of occasions but are performed generally by one or various bertsolaris onstage in an event arranged for the purpose or as a sideshow, in homage ceremonies, in benefit lunches and suppers, with friends or at a competition. Such a sung piece of composition is called a bertso, the person who sings it is called a bertsolari and the art of composing bertsos is called bertsolaritza in Basque. Traditionally these were sung by men but there is an increasing number of young female bertsolaris today.
Usually the Basque terms are used in Spanish and French but the Spanish terms versolarismo and bertsolarismo and the French terms bertsularisme (from Zuberoan bertsularitza), bertsolarisme and versification are also used.