Context can be critical to poetics and to the development of poetic genres and forms. For example, poetry employed to record historical events in epics, such as "Gilgamesh" or Ferdowsi's "Shahnameh", will necessarily be lengthy and narrative, while poetry used for liturgical purposes in hymns, psalms, suras and hadiths is likely to have an inspirational tone, whereas elegies and tragedy are intended to invoke deep internal emotional responses. Other contexts include music such as Gregorian chants, formal or diplomatic speech, political rhetoric and invective, light-hearted nursery and nonsense rhymes, threnodies to the deceased and even medical texts.