1. Apparatus for acting-upon compositions that contain a sound component, the apparatus comprising: one or more processors configured to: obtain or provide, an ordering of a plurality of compositions and sound-segments, including a current-location in said ordering; wherein two or more different sound-segments are associated with each composition in said ordering; change the current-location in said ordering, in response to each user navigation action; play the sound-segment that is associated with the current-location in said ordering, in response to each change to the current-location. act-upon the composition that is associated with the current-location in said ordering, in response to a command-action by the user.