Martin (1992: 523):
Tenor refers to the negotiation of social relationships among participants.
This confuses context (tenor) with language (negotiation). The confusion is thus along the theoretical dimension of stratification. Halliday & Matthiessen (1999: 320) describe tenor as:
the relationship between the interactants, between speaker and listener, in terms of social rôles in general and those created through language in particular (‘who are taking part?).