As the population grows older, it is increasingly important to address the challenges associated with aging, such as health decline and loss of independence.Exercise can help seniors remain physically fit, but seniors often are unable to exercise regularly because of barriers and lack of motivation. Current research suggests that music making may provide health benefits and motivate individuals to exercise. This interdisciplinary study combines the fields of music making and design in relation to aging in order to address the question of how design can be used to create devices for seniors to make music, creating a more positive exercise experience. The topic was explored using qualitative design research methods. Music making devices were used as technology probes in a seniors' fitness class, an expert interview was conducted with a fitness instructor, and a co-design workshop was held with seniors. The findings suggest that music making can influence the participants' behaviour in a fitness class and could be used to motivate seniors to exercise. Based on the research, several design recommendations were made concerning the sensory aspects of the object, such as the audio and visual feedback and the tactile experience, and the usability and features of the product.