Have you ever been meandering through Brooklyn and come across a CD jewel case with a hand-drawn cover and thought to yourself, What the heck is that? If so, you may have stumbled upon Dylan Samson’s Mixtape Series. Samson burns mixed CDs, adorns them with artwork and poetic titles, and leaves them somewhere in New York for strangers to find. You can find the locations on his website. He’s been doing this for years and is up to volume 59. The most recent CD, called “Waiting Can Be Painful,” was dropped off on Degraw Street in Gowanus this morning and includes songs by Public Service Broadcasting, LCD Soundsystem, Run the Jewels, Thundercat, etc. There was a hidden book project not unlike this in summer of 2013, when book began popping up in public locations, such as the nooks of park benches. That became a sort of enigmatic treasure hunt for bibliophiles. Maybe this will be the same thing for audiophiles.