About pitch in speech [must]

Hi,In [He that would the daughter win {must} with the mother first begin.], [must] still acts as a judgment to say [first begin with the mother] is necessary for him to win the daughter. So, [must] here is like a sentence of judgment after the main sentence. As this way:......you first begin with the mother. That needed for him to win the daughter. So, the pitch of the [must] is the same as the [may] in [Truth {may} sometimes come out of the devil's mouth.] [must] and [may]------all act as a judgment, so their pitch are lower than all the rest words???I need your help. Thank you for your assistance.