The FAAB (Feedback-Actuated Augmented Bass) is a modi ed double bass featuring electromagnetic pickups, an embedded speaker and onboard DSP through a Bela microprocessor. Through mechanically induced feedback and adaptive signal processing, the instrument expands the textural and spectral properties of traditional as well as extended playing techniques. The complex dynamics of the electro-acoustic couplings requires the performer to investigate human-instrument relationships from the perspective of negotiation and exploration rather than instrumental mastery. The improvised performance is a snapshot of the continuous co-evolution between, on the one hand, new techniques and performance practices and on the other, mechanical, acoustical and digital optimisation.