Electronic stethoscopes address limitations of auscultation with analog stethoscopes, such as the dependency on the physicians{\textquoteright} hearing ability, their experience, and their subjective interpretation. However, electronic stethoscopes currently found on the commercial market fail to exploit the full potential of cutting-edge microphone technology and innovative multi-sensor approaches. Our novel device, called Open-source Modular Electronic Stethoscope (OMES), proposes a modular upgrade to an analog stethoscope that incorporates multiple sensor types and features microphone array capabilities. OMES has been tested for its performance in detecting heart beats but is designed to be applied to other auscultation sites as well. Above that, it can be employed as an educational and potential research platform to promote the development of revolutionary signal processing techniques and artificial intelligence algorithms.