His major research interests include systemic functional linguistics, discourse analysis, systemic phonology and social semiotics. Within discourse analysis, David has applied appraisal theory to a range of language contexts, including post-match interviews with footballers, medical consultations with hospital patients suffering depression and popular rap music. Following in the tradition of social semiotics, he has also examined the meaning-making potential of sound, with a specific focus on the semiotics of performance voices in popular music.