This paper presents a pioneer study of speech pro-sody and musical prosody in modern popular music, with a specific attention to music where the voice is closer to speech than to sing. The voice in music is a complex system in which linguistic and musical systems are coupled and interact dynamically. This paper establishes a new definition of the musical prosody in order to model the specific relations between the voice and the music systems in this kind of music. Additionally, it presents a methodology to measure the musical prosody from the speech and music signals. An illustration is presented to assess whether the speech prosody and the musical prosody can characterize the phonostyle of a speaker, by comparison of three American-English rappers dating from the beginning of the 2000's. The main finding is that not only the rappers can be characterized and distinguished by their speech prosody, but also by their musical prosody, i.e. by the degree of synchronization between their lyrics with the musical system.