Give it a tree — as an indented outline, a JSON or XML file, or drawn by clicking — and hear its shape. A node's depth sets its register (the deeper it sits, the higher it sounds), siblings under one parent stack as chord tones, and the traversal order becomes the phrase: depth-first dives down each branch before moving on, while breadth-first terraces the tree level by level. Turn on harmony and each family of siblings strikes together as a chord. This is the L-system grower's sibling — for trees you hand it, rather than trees it grows.