A system and method for online collaboration of synchronized audio and video data from multiple users through an online browser is disclosed. An online network environment (e.g., online social media platform) that is accessible by users through an online browser includes an online player/recorder that is capable of playing back multiple audio and video data uploaded by multiple users in real time, and to change tempo while maintaining the original audio key or change pitch while maintaining the original tempo during playback. The platform captures playback positions of audio data based on the corresponding playback positions of video data. The platform includes a synchronizing algorithm that calculates the discrepancies between audio playback positions and the corresponding video playback positions so that the audio and video data play in synchronization.