This work explores the topic of digital audio signal processing for modular synthesizers and the design of digital oscillator for modular standard known as Eurorack. Introduction of the theoretical part is dedicated to basic terms and blocks used in modular synthesizers. The thesis also characterizes and presents the methods of sound synthesis. The second part of the theory concerns analog and digital signal conversion made by digital signal processors DSP, focusing on ARM with focus on ARM architecture. The practical part of the thesis concerns design and construction of the digital oscillator which generates periodic waveforms without aliasing distortion. The oscillator also allows several types of modulations and waveforming and the module has several inputs for connecting control voltages or external audio signals.