Beth's musical genre is post-punk because post-punk is a genre that emerged in the late 1970s and early 1980s as a response to the punk movement. It is characterized by its experimental and avant-garde approach, combining elements of punk rock with influences from various other genres such as art rock, funk, and reggae. Post-punk often features dark and introspective lyrics, angular guitar riffs, and unconventional song structures. Based on this description, it can be inferred that Beth's musical genre is post-punk.