With the understanding also (kai twi no). Instrumental case of nou. Paul is distinctly in favour of the use of the intellect in prayer. Prayer is an intelligent exercise of the mind. And I will sing with the understanding also (psalw de kai twi no). There was ecstatic singing like the rhapsody of some prayers without intelligent words. But Paul prefers singing that reaches the intellect as well as stirs the emotions. Solos that people do not understand lose more than half their value in church worship. Psallw originally meant to play on strings, then to sing with an accompaniment ( Ephesians 5:19 ), and here apparently to sing without regard to an instrument.