Scalability and miniaturization are hallmarks of solid-state platforms for photonic quantum technologies. Still a main challenge is two-photon interference from distinct emitters on chip. This requires local tuning, integration and novel approaches to understand and tame noise processes. A promising platform is that of molecular single photon sources. Thousands of molecules with optically tuneable emission frequency can be easily isolated in solid matrices and triggered with pulsed excitation. We here discuss Hong-Ou-Mandel interference experiments using several couples of molecules within few tens of microns. Quantum interference is observed in real time, enabling the analysis of local environment effects at different time-scales.