Abstract: An electronic device with one or more processors and memory detects a user input to play a media item, where the media item is associated with at least a portion of an audio track and one or more media files. The device requests the media item from a server in response to the user input and, in response to the request, receives, from the server, the one or more media files and information identifying at least the portion of the audio track. The device obtains at least the portion of the audio track based on the information identifying at least the portion of the audio track. The device also displays the one or more media files and, while displaying the one or more media files, plays back at least the portion of the audio track in synchronization with the one or more media files.

Abstract: An electronic device with processor(s), memory, and a touch screen display presents a media item, where the media item is associated with a metadata structure that includes first information identifying at least a portion of an audio track, second information identifying one or more media files, and third information identifying one more audio and/or video effects. The presenting includes: displaying one or more media files associated with the media item; and playing back at least a portion of an audio track associated with the media item in synchronization with the one or more media files. While presenting the media item, the device: detects a touch input gesture; and, in response to detecting the touch input gesture, applies an audio and/or video effect specified by the third information to the audio track being played back and/or at least a portion of the one or more media files being displayed.

Abstract: An electronic device with one or more processors and memory displays a first user interface including a plurality of audio tracks, detects a first user input selecting one of the plurality of audio tracks, and, in response to detecting the first user input, displays a second user interface for recording a video clip. The device also detects a second user input to initiate recording of the video clip and detects a third user input to stop recording of the video clip. The device further detects a fourth user input to publish the media item based on the video clip and the selected audio track and, in response to detecting the fourth user input, publishes the media item to a server, including sending to the server information identifying the selected audio track, the video clip, and information related to synchronization of the selected audio track and the video clip.

Abstract: A server system with one or more processors and memory maintains a database for a plurality of root media items, where: a respective root media item is associated with a family tree that includes a genesis node and multiple leaf nodes; and the genesis node corresponds to the respective root media item and a respective leaf node of the multiple leaf nodes corresponds to a first modified media item that is a modified version of the respective root media item. The server system: receives at least a portion of modified metadata corresponding to a second modified media item that is a modified version of a media item corresponding to a respective node in the family tree; and, in response, appends, to the family tree, a new leaf node that is linked to the respective node, where the new leaf node corresponds to the second modified media item.