Abstract: A computer method and apparatus to “digitize” and simulate the classroom lecturing is disclosed. A teacher can use the apparatus to draw on a web page or on a computer whiteboard with extensible size, dynamically insert (delete) image and text objects into (from) the whiteboard or the web page, and record voice narration at the same time. The apparatus stores these activities into a multiplexed data stream and a header stream. The combination of streams and the annotated web page is called an audio-graph (AG) item. Users could save the streams to a file, e-mail it, or upload it to a web site for streamed playback. The apparatus is a system of authoring, playback, organize, and indexing the AG items. The data stream of an AG item comprises (compressed) audio frames, (compressed) stroke frames, image and text frames. The header stream comprises information messages, and event messages (with timing) that are used to control the display (window) during playback.