The Melodist is a 3rd-tier class introduced in Valkyria Chronicles 2. They can be promoted from Anthem Corps as part of the Engineer Class Tree. As opposed to anthem corps and anthem elites, their musical instruments (called Orchestral) have the ability to inflict status ailments on enemies. They also have better attributes than anthem corps.
Melodists did not appear in Valkyria Chronicles.
Valkyria Chronicles 2
Melodists can be promoted from Anthem Corps as part of Engineer Class Tree. The credit requirements for changing a unit's class into a Melodist are: Diploma x1, Attack X x1, ArmsII x1, AttackII X x1
Valkyria Chronicles 3
In Valkyria Chronicles 3, the role of melodist and its two branching classes are assimilated back into the engineer class. Engineers are now capable of equipping orchestrals when they class up to engineer elites.
The GRA have no known Melodists.