POLYPHONIC AUDIO KEY FINDING USING THE SPIRAL ARRAY CEG ALGORITHM (WedPmOR2)

Author(s) : Ching-Hua Chuan (University of Southern California, United States of America) Elaine Chew (University of Southern California, United States of America)

Abstract : Key finding is an integral step in content-based music indexing and retrieval. In this paper, we present an O(n) real-time algorithm for determining key from polyphonic audio. We use the standard Fast Fourier Transform with a local maximum detection scheme to extract pitches and pitch strengths from polyphonic audio. Next, we use Chew¡¯s Spiral Array Center of Effect Generator (CEG) algorithm to determine the key from pitch strength information. We test the proposed system using Mozart¡¯s Symphonies. The test data is audio generated from MIDI source. The algorithm achieves a maximum correct key recognition rate of 96% within the first fifteen seconds, and exceeds 90% within the first three seconds. Starting from the extracted pitch strength information, we compare the CEG algorithm¡¯s performance to the classic Krumhansl-Schmuckler (K-S) probe tone profile method and Temperley¡¯s modified version of the K-S method. Correct key recognition rates for the K-S and modified K-S methods remain under 50% in the first three seconds, with maximum values of 80% and 87% respectively within the first fifteen seconds for the same test set. The CEG method consistently scores higher throughout the fifteen-second selections.

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