mas.kil is a noun used as a designation in the opening material of psalms.

The attested use is a psalm-opening designation: the singular absolute noun occurs in opening material where the APB sometimes explicitly retains “Maskil,” including headings linked with David or Asaph and an opening call to instruction.

1. Psalm-opening designation · dominant

   In Psalm 32:1 the APB renders the opening, “Of David. A Maskil,” before the statement about forgiven transgression. In Psalm 54:1 it renders “To the conductor, with music; a Maskil of David” before the prayer for salvation, while Psalm 78:1 has “A Maskil of Asaph” before the speaker calls the people to hear instruction. The supplied morphology is consistently a common masculine singular absolute noun.

   Psalm 32:1Psalm 52:1Psalm 54:1Psalm 74:1Psalm 78:1Psalm 89:1

In the Anselm Project Bible: The APB explicitly retains “Maskil” in several openings, such as “A Maskil of Asaph” in Psalm 78:1 and “a Maskil of David” in Psalm 54:1. In other supplied verses the term's specific contribution is not separately visible in the translation.