The note can be found in the Jamaica Plain Town Hall basement next to a terminal in the treasures exhibit.
This is a Holotape.
Holotapes are laser-readable media storage devices. In 2077, we used Holotapes to record audio and data files, like music, journals, even games. While this may seem primitive to you, two hundred years in the future, this was a common and popular technology in our time.
You can play holotapes with the Terminal on this table. Press the 'Load' button, insert the Holotape into the slot, and close it. It should play automatically.