Many poets feeling their way around free verse find themselves trapped by its relative lack of constraint. That is to say, they find themselves using formal elements that the form lends itself to very well, and even perfecting them, while remaining somewhat dissatisfied with the musicality in the work. The result can often be frustrating, as these kinds of poems are gems in many ways, and often sound fantastic when read aloud while being elegantly pruned constellations of detail on the page.
Establishment and Improvisation
The key to making the musicality pop out of free verse is to establish expectations or ground rules in the opening stanza, and then to embellish and ornament them as you go. This can be by building up linguistic structures that follow familiar rhythmic patterns, such as an iambic flow or a meter that you can fold and manipulate as you go. Once the pattern is constructed, it can be imported into different techniques and rotated to provide opportunities for change. For instance, if you are running an iambic flow and you are looking to move into a new pattern, breaking your last foot of a middle line in the stanza where you make the change can allow you to pivot to the resulting accent pattern in the next paragraph.
Numeric progressions can also be a big help. Working in sets of three or four and passing patterns at points of change is a popular move in many kinds of performance poetry. For example, repeating a rhyme scheme four times before using four of the same accented vowels in a row to gloss over the fact that the rhyme scheme has been dropped, and then landing back into a new rhyme on the other side of the feat. By rotating these techniques in conjunction with each other, a polyrhythmic structure free of entanglement with absolute rules or form can rise out of the relative emptiness of a free structure.
Notation and Cadence
If you are looking to make a free style pop, one way is to commit to a line length that is measured in something other than simple syllables. Since musicality is the main organizing principle in this particular exercise, mine it for more ways to use the language. Constructing lines around length of delivery time, using punctuation consistently to notate measured lengths of pauses, and spacing the poem so that the distance between words reflects their relative lengths are all organizing principles that can replace the standard rhythmic and metric constraints found in traditional poetic styles with a more open-ended approach to structure, one that allows the poet to use the organizing principle itself as a way of establishing their skills to the audience.