respective timelines 411 412 431 432 are shown using the example mentioned previously to aid in the understanding of the invention the viewer window 410 displays a clip of a critic explaining certain motions of a dance choreography the first timeline 411 of the viewer window corresponds to the video feature of the clip and the second timeline 412 of the viewer window 410 corresponds to the audio feature of the clip the canvas window 430 displays a clip of the actual dancing choreography the critic is commenting on similarly the first timeline 431 of the canvas window 430 corresponds to the video feature of the clip and the second timeline 432 of the canvas window 430 corresponds to the audio feature of the clip it is desired that when the critic starts to comment on certain sequence of the dance movements the video of the critic be replaced by the actual video of the dance movements while the comment made by the critic continues as the critic is finished with the comment the audio be replaced by the audio corresponding to the dance movements in this example the video in point 413 and the audio in point 415 are positioned using the pointing arrow 450 in the respective timelines 411 412 in which the video and the audio clips are to start the pointing arrow 450 is then moved to position the video out point 414 in which the critic is about to comment on the particular dance movement the pointing arrow 450 is moved once more to position the audio out point 416 in which the critic finishes making the comment on the movement in one embodiment the pointing arrow 450 is then moved.