This thesis project in integrated product design focuses on developing a musical instrument to complement the standard inventory at social jam sessions, facilitating music novices' participation. Social jam sessions are defined as informal, unrehearsed music gatherings accommodating musicians of varying skill levels, emphasizing social interaction rather than performance. Research indicates that such activities positively impact mental wellbeing and social development, offering potential to address issues of declining happiness and increasing loneliness among young adults in the Netherlands. Observations and a poll conducted with young adults at TU Delft revealed that beginners seldom participate in or return to social jam sessions, primarily due to challenges related to musical instruments. Consequently, the project targeted instrument design as a key area for innovation. Employing a user-centered, iterative research through design methodology, the project involved multiple design cycles of prototype development, user testing, and refinement based on feedback. The project was structured into three design sprints: understanding the problem, defining a design direction, and developing a functional prototype. Through this process, one experimental setup and five prototypes were created, supplemented by desk research on relevant design artifacts. The resulting instrument, the "Bass Box," is a one-string acoustic bass with a moveable bridge, designed to resemble a cajón in size and playing position. The instrument allows dynamic pitch changes by adjusting the bridge, with note markers and an integrated tuner providing orientation for novices. The Bass Box bridges the gap between simple percussive instruments and complex melodic instruments, enabling harmonic improvisation and enriching acoustic jam sessions with audible bass notes.