A speaker brings the carved head of a viol, the scroll at the top of the instrument, to the person who made it. That's the simple scene. Everything else comes from the way the poem plays with words. The maker's "name is wise," which suggests he's trusted, someone who knows his craft. He "deals in sound," and the speaker calls him a "pitch merchant," a phrase that mixes music (pitch) with the language of trade, and maybe a hint of tar or salesmanship too.
The last line, "here for some high words," works two ways. It can mean high notes, the top of the instrument's range, or it can mean a quarrel, since "high words" is an old phrase for angry talk. The poem seems to enjoy keeping both meanings alive.
The mood is light, dry, and a little playful. The speaker comes across as a devoted enthusiast, in keeping with the title, who treats the maker with affectionate respect.