Dave Bonta's poem is only four short lines, but it sets up a whole scene: a quiet dinner where the speaker sits down not with people but with two feelings, hope and doubt. Instead of treating them as enemies, the speaker keeps them as company. The "coat of velvet" suggests something soft, formal, even a little luxurious, as if this uneasy meeting is dressed up and made comfortable.
The second half turns to light and sound. "Half moon, half dark" gives a picture of something unfinished, partly lit and partly shadowed, which fits a mind that can't settle on certainty or despair. Then the speaker says "we sing bass and treble," so the three of them blend into one song, low notes and high notes working together. The mood is calm and accepting rather than anxious. The poem seems to suggest that hope and doubt can coexist, and that living with both may make a fuller kind of music than either could alone.