Audio key finding: Considerations in system design and case studies on Chopin's 24 preludes

We systematically analyze audio key finding to determine factors important to system design, and the selection and evaluation of solutions. First, we present a basic system, fuzzy analysis spiral array center of effect generator algorithm, with three key determination policies: nearest-neighbor (NN), relative distance(RD), and average distance (AD). AD achieved a 79% accuracy rate in an evaluation on 410 classical pieces, more than 8%higher RD and NN. We show why audio key finding sometimes outperforms symbolic key finding. We next propose three extensions to the basic key finding system - the modified spiral array (mSA),fundamental frequency identification (F0), and post-weight balancing (PWB) - to improve performance, with evaluations using Chopin's Preludes (Romantic repertoire was the most challenging).F0 provided the greatest improvement in the first 8 seconds, while mSA gave the best performance after 8 seconds. Case studies examine when all systems were correct, or all incorrect.