Expressive characterization of flamenco singing intends to analyze the main differences between performances, players, playing styles and emotional intentions. This work addresses the characterization of expressive flamenco singing performances in two stages: first, a qualitative approach interviewing flamenco experts to get hints of what are the main particular aspects of flamenco singing and then, a second approach comparing audio recordings of the same melodies sung in both flamenco style and in their original styles (classic, Cuban folk and jazz) by a professional singer. This research intends to provide a characterization of flamenco singing based on acoustic analysis of audio recordings and feature extraction such as energy, pitch, flatness, hfc, spectral roll-off, etc.