IRCAM has a long experience in analysis, synthesis and transfor- mation of voice. Natural voice transformations are of great inter- est for many applications and can be combine with text-to-speech system, leading to a powerful creation tool. We present research conducted at IRCAM on voice transformations for the last few years. Transformations can be achieved in a global way by mod- ifying pitch, spectral envelope, durations etc. While it sacrifices the possibility to attain a specific target voice, the approach al- lows the production of new voices of a high degree of naturalness with different gender and age, modified vocal quality, or another speech style. These transformations can be applied in realtime using ircamTools TRAX. Transformation can also be done in a more specific way in order to transform a voice towards the voice of a target speaker. Finally, we present some recent research on the transformation of expressivity.