6. A computer-implemented method outputting first content and second content, the computer-implemented method comprising: under control of one or more computing devices, causing output of a first content and a second content; maintaining, based at least in part on synchronization information, synchronization between an output pointer of the second content and an associated position of the first content, wherein the associated position of the first content advances during output of the first content, and wherein the output pointer indicates a position within the second content corresponding to a current output position of the first content; obtaining, from an input device, an input pointer referencing a position within the second content being presented; during advancement of the output pointer, determining, independent of the obtained input pointer, a position of the output pointer corresponding to the current output position of the first content; determining a lead interval based at least in part on a difference between the determined position of the output pointer and the position of the second content referenced by the input pointer; and modifying an attribute associated with the output of the first content based at least in part on the determined lead interval.
6. A computer-implemented method outputting first content and second content, the computer-implemented method comprising: under control of one or more computing devices, causing output of a first content and a second content; maintaining, based at least in part on synchronization information, synchronization between an output pointer of the second content and an associated position of the first content, wherein the associated position of the first content advances during output of the first content, and wherein the output pointer indicates a position within the second content corresponding to a current output position of the first content; obtaining, from an input device, an input pointer referencing a position within the second content being presented; during advancement of the output pointer, determining, independent of the obtained input pointer, a position of the output pointer corresponding to the current output position of the first content; determining a lead interval based at least in part on a difference between the determined position of the output pointer and the position of the second content referenced by the input pointer; and modifying an attribute associated with the output of the first content based at least in part on the determined lead interval. 11. The computer-implemented method of claim 6 , wherein maintaining, based at least in part on the synchronization information, synchronization between the output pointer of the second content and the associated position of the first content comprises updating the output pointer of the second content to correspond to the associated position of the first content during output of the first content.