Digital pen technology has allowed for the easy transfer of pen data from paper to the computer. However, linking handwritten content with the digital world remains a hard problem as it requires the translation of unstructured and highly personal vocabularies into structured ones that computers can easily understand and process. Automatic recognition can help to this direction, but as it is not always reliable, solutions require the active cooperation between users and recognition algorithms. This work examines the use of portable touch-screen devices in connection with pen and paper to help users direct and refine the interpretation of their strokes on paper. We explore four techniques of bimanual interaction that combine touch and pen-writing, where user attention is divided between the original strokes on paper and their interpretation by the electronic device. We demonstrate the techniques through a mobile interface for writing music that complements the automatic recognition with interactive user-driven interpretation. An experiment evaluates the four techniques and provides insights about their strengths and limitations.