SoundCloud is supposed to be an audio platform, but watching it play back your favorite new jam can be just as rewarding as listening to it. Ever since a big redesign two years ago, the signature wave of orange that travels across the songs waveform has been accompanied by little pop-up comments from fellow users of the service. Unlike the vitriolic lambasting of YouTube, however, here you are treated to a charmingly innocent torrent of positivity and approval. Every website and service wants to be social, but only a few have managed to turn that into an asset rather than a burden.