1. A method comprising: training, at a user terminal, a first voice conversion model with respect to a training source speech of a first speaker and a second voice conversion model with respect to a training target speech of a second speaker; wherein training the first voice conversion model further comprises determining a first conversion function for transforming any source speech into corresponding synthetic speech, the first conversion function receiving the training source speech of the first speaker and a training source synthetic speech of the first speaker as inputs, and wherein training the second voice conversion model further comprises determining a second conversion function for transforming synthetic speech into corresponding target speech, the second conversion function receiving the training target speech of the second speaker and a training target synthetic speech of the second speaker as inputs, and wherein said training target synthetic speech is produced from said training target speech; processing, at the user terminal, source speech of the first speaker using the first voice conversion model to convert the source speech to synthetic speech; and processing, at the user terminal, an output of the first voice conversion model at the second voice conversion model to produce target speech corresponding to the source speech.