I present a recent analytic solution (Horak & Abramowicz 2021, unpublished) that describes quasi-normal modes of super-compact stars close to the Bondi limit. In the LIGO-Virgo terminology these are wave-fronts and frequencies of ringdowns and echoes. The new results will help distinguishing between black hole versus non black hole origin of the waves. They may also constrain some quantum-gravity ideas about the quantum black hole alternatives, like firewalls and gravastars.