i started with simply line drawing where i only focus on the flow of their movement and not so much on anatomy
then i added value to create composition: a tree casts a shadow and darkens the silhouette of the people - i like to use a bright background to make their silhouette pop (by putting a far away landscape there)
then i added color - green to give a soothing nature look and contrast it with red fabric to draw attention to the focal point
also i added a 5th musician to fill out the gap and create a more contineous flow from one person to a another
working out the goddamn tree tho... oh and i decided to place a waterfall in the background because it fills the air with fog which goes well against the larger amount of detail in the foreground
some fore-foreground stuff to create more depth
lastly i opened the comp up a bit more, the tree was hands down to small, more background, more detail and birds