A method of generating a message having an invariable portion (U1) and a variable portion (V) is provided. Most of the invariable portion (U1) is provided in the form of recorded speech (A) whereas the variable portion (V) is provided in the form of synthesised speech (B). The synthesised speech (8) also extends by half a phoneme into the invariable portion (U1) of the message. The synthesised speech (B) and the recorded speech (A) are then concatenated, with a transition signal being formed on the basis of a boundary portion of each of the recorded (A) and synthesised signals (B) about any join (8). In forming the transition signal, a set of transition signal pitchmarks is created and an overlap-add technique is used to copy the waveform within the boundary portions of the speech signals (A, B) around the transition signal pitchmarks. The signal around the penultimate pitchmark in the leading boundary portion is copied to the trailing half of the transition signal and the signal around the second pitchmark in the trailing boundary portion is copied to the leading half of the transition signal. In this way, the characteristics of the generated message around the join (8) change gradually between the characteristics of the recorded speech (A) and the characteristics of the synthesised speech (B).