ProGress (Prolongation-enhanced DiGress) is a novel symbolic music generation framework that integrates Schenkerian analysis with discrete graph diffusion models. Unlike existing black-box generative systems, ProGress emphasizes musical interpretability and structural cohesion. It adapts the DiGress discrete diffusion model for symbolic phrase generation, introduces a Schenkerian-inspired phrase fusion methodology, and allows controllable generation of harmonically and melodically coherent compositions. Through blinded human subject experiments, ProGress significantly outperforms prior state-of-the-art models and even surpasses Bach chorales in enjoyability metrics, despite using orders of magnitude fewer parameters (~3M vs. 500M+).