I wish there were a simple way to sample the newest music in the Pandora library. If there is such a way I don't know about it. Hope others can shed some light on this.
Some of us have the opposite problem: putting new music out there and trying to get listeners. Hang in there!
This is a good question.
Maybe not exactly what you are looking for, but a couple options would be checking out the New Music stations and suggestions Pandora has available here: https://www.pandora.com/browse/music/new-music
Also, the new "Pandora Modes" feature has a "newly released" filter option for all your prexisting stations. You can learn about that feature here: https://help.pandora.com/s/article/Pandora-Modes?language=en_US
Hope these options help!