Some features of epistemic modal logic are in debate. They may be viewed as a family of substructural or modal logics. Confusing modality is known as the modal fallacy. A formal modal logic represents modalities using modal operators. Music prior to 1600 was modal rather than tonal. Traditional folk music provides countless examples of modal melodies. Sentences using modal verbs place the infinitive at the end. Open tunings may be "chordal" or "modal". He believed that terms such as "tonal", "modal" and "serial" are misleading analytical conveniences. Old Japanese verbs used inflection for modal and conjunctional purposes. For details of the uses of modal verbs, see English modal verbs. The verb that is immediately subordinate to the modal is always an infinitive. For details about modal auxiliaries, see English modal verbs. A well known user of modal tunings is Sonic Youth. The music combines elements of hard bop and modal jazz.