An experimental investigation is done to study thermoacoustic characterization of syngas fuels for different compositions of syngas, and this was compared with synthesis natural gas. The laboratory scaled bluff body type combustor was fabricated with a power rating of 30KW. The chemical composition of syngas was varied from CO/H2 ratio from 0 to 95% of CO in a step of 5%. For the chosen cases, simultaneous pressure and time-resolved OH* chemiluminescence were recorded. Further, OH* chemiluminescence fluctuations are qualitatively analyzed to compare the acoustic characteristics of H2–CH4 and H2–CO. The mean flame structure was investigated to study the difference in the combustion instability mechanism due to fuel composition. © 2021, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.