This study arises out of Broughton's (1965) pilot work on song modification in some European bush crickets. It describes the range of changes in song that occur in Platycleis intermedia, when confined in the same recording cage as a singing congeneric. The modifications ranged from complete inhibition of singing, through various degrees of duetting interaction, to a change in echeme length to one outside the normal repertoire. These acoustic interactions are discussed in terms of similarities and differences in song components of the interacting species, as well as in terms of their natural tendency to react to another song as if it were produced by a conspecific singing nearby. The interactions in P. intermedia are discussed in the wider context of song modification.