Simple ternary form In ternary form each section is self-contained both thematically as well as tonally (that is, each section contains distinct and complete themes), and ends with an authentic cadence. The B section is generally in a contrasting but closely related key, usually a perfect fifth above or the parallel minor of the home key of the A section (V or i); however, in many works of the Classical period, the B section stays in tonic but has contrasting thematic material. It usually also has a contrasting character; for example section A might be stiff and formal while the contrasting B section would be melodious and flowing.
simPLE tERnary forM IN TerNarY foRm eACh sECtIOn is SeLf-contained botH tHematicaLLy as well as toNaLly (that iS, EaCh Section coNTAins diStincT and coMplEtE theMes), aNd eNDs With an authentic cADencE. The b sectiOn Is GENerAlLy in a cOntRasTinG but closeLy relaTed keY, usually a pERfect fiFth aBOVE or The PARalLeL minOr of The hOMe kEY of the a sECtiOn (v or I); hOwEver, in Many wOrks Of the classiCaL period, thE B section stAYs iN tonic bUT has COnTrasTing ThEMatiC MAtErial. it usually also haS a COnTrasTINg CHaRactEr; for eXAmple sECtiOn A miGht Be stifF aND FORmal WhiLe ThE coNtrAstiNg b seCTIon WOUlD Be MelodiOus aNd fLoWINg.