In this paper we address the expressive control of singing voice synthesis. Singing Voice Synthesizers (SVS) traditionally require two types of inputs: a musical score and lyrics. The musical expression is then typically either generated automatically by applying a model of a certain type of expression to a high-level musical score, or achieved by manually editing low-level synthesizer parameters. We propose an alternative method, where the expression control is derived from a singing performance. In a first step, an analysis module extracts expressive information from the input voice signal, which is then adapted and mapped to the internal synthesizer controls. The presented implementation works in an off-line manner processing user input voice signals and lyrics using a phonetic segmentation module. The main contribution of this approach is to offer a direct way of controlling the expression of SVS. The further step is to run the system in real-time. The last section of this paper addresses a possible strategy for real-time operation.