"Mor lam" was traditionally sung in the Lao or Isan language. The subject matter varied according to the genre: love in the "lam gon" of Ubon; general knowledge in the "lam jot" of Khon Kaen; or Jataka stories in "lam phun". The most common verse form was the four-line "gon" stanza with seven main syllables per line, although in Khon Kaen the technical subject matter led to the use of a free-form series of individual lines, called "gon gap". In Laos, it is the regional styles which determine the form of the text. Each style may use a metrical or a speech-rhythm form, or both; where the lines are metrical, the "lam" styles typically use seven syllables, as in Isan, while the "khap" styles use four or five syllables per line. The slower pace of some Lao styles allows the singer to improvise the verse, but otherwise the text is memorised.