LifeAndFire
I love the marimba sound.
Whats is missed? the counterpoint, you most "full" the chords, when you do a melody, think that the instrument that do it and the instrument that accompaniment it mos be complete the cord, example, if a do in the marimba: c, d, e, f, e, d, g, f, a
and in the clarinete: c, d, e, f, e, d, g, f, a (the same) dont do it, maby with a third it can. the point is that you most give variety to the piece, never do that the instruments do the same note and th same rhythm, because sounds void. maybe can work more if you join an instrument that do a accompaniment, like a strings chord or a melodic one doing an accompaniment, like (in doubles in c chord) c, g, e, g
or i dont know, some like this.

Well, see you ^^