Natural voice transformation will reduce the need for authentic voices in many situations, ranging from vocal services via education and entertainment to artistic applications. Transformation of one voice to correspond to that of another person has been studied for decades but still suffers from limitations that we propose to overcome by an alternative approach. It consists in modifying pitch, spectral envelope, durations etc. in a global way. While it sacrifices the possibility to attain a specific target voice, the approach allows the production of new voices of a high degree of naturalness with different sex and age, modified vocal quality (soft, breathy, and whisper), or another speech style (dullness and eagerness). The transformation of sex and age has been evaluated by a listening test.