Slackbox - Spotify playlist collaboration through Slack
RightGIF - Less noise, better GIFs. A better /giphy for Slack.
Brain.fm - Music designed for the brain to enhance focus, relaxation, meditation, naps and sleep within 10 - 15 minutes of use.
Yarn for Slack - Drop TV and movie clips into your Slack chats
SoundCloud - Enjoy music & follow favourite artists
Firesong - Giphy for Music in Slack w/ Emoji Search