solution, the five compounds are UV fluorescent emitters with very narrowband emission. The differences in the energy of emission between the five compounds is driven by changes in LUMO level as the position and number of pyridine N substitution changes, while the HOMO level remains largely insensitive to these structural changes. The greatest stabilisation of the LUMO, and therefore the lowest energy of emission, is seen in 6,10NICz, followed by 6NICz, 4NICz, 5NICz and finally 7NICz. PMMA films doped with 0.1, 1 and 10 wt% of the different emitters show biluminescence at room temperature, with distinct fluorescence and phosphorescence bands. Additionally, the two metasubstituted emitters 6NICz and 6,10NICz show multi-resonant thermally activated delayed fluorescence at 1 wt% doping, with 6,10NICz also exhibiting MR-TADF at 10 wt%. This is, to the best of our knowledge, the first unequivocal demonstration of MR-TADF/RTP type biluminescence in an organic emitter. The RTP persists even at very low-doping concentrations and so is monomolecular in nature. We note that the discovery of MR-TADF/RTP biluminescence in this family of emitters suggests a number of exciting applications for future research, including the sensing of oxygen and/or temperature, and broad-spectrum emission.