A method of generating a stream comprising synchronized interactive content is described. The method comprises the steps of: transmitting a first stream from a studio to a terminal or a terminal system of a first user and to a buffer; transmitting in response to the first stream a second stream to a mixer connected to the buffer, the second stream comprising content generated in reaction to the content of the first stream; providing the mixer with a temporal relation between the packets in the first and second stream; generating a first output stream comprising a substantially synchronized content by mixing packets in second stream with packets of the buffered first stream on the basis of the temporal relation.

A playing controller includes: a data acquiring unit configured to acquire audio data associated with information regarding a play position in a music piece and text-related data associated with the information regarding the play position; an operation signal acquiring unit configured to acquire an operation signal indicating an operation for a control of the music piece; an audio data processing unit configured to process, in accordance with the operation signal, the audio data associated with a section within the music piece identified by the information regarding the play position; an image data generating unit configured to generate image data containing a character image based on the text-related data and process the character image showing a lyric in the section based on the information regarding the play position and the operation signal; and a data output unit configured to output the processed audio data and the image data.