The goal of this work is to develop a framework of intelligent computer-aided composition based on melodic contours and tabular constraints. Melodic contour is derived from whistling input as a MIDI controller. Tabular constraint is a flexible representation for describing, processing, and synthesizing musical structure of MIDI format music. Based on a given melodic contour, there are two main areas of computer-aided composition to be treated: melody variation and harmonization. We develop a musical plan representation called tabular constraints to allow the interactive experimentation for those two composition activities. A set of transformation operators is available for automatic composition. We have demonstrated that the integration of melody transcription and tabular constraints can allow a user to easily explore his potential in melody creation and harmonization.