Music is certainly a fantastic way to help one get into the mindset of a particular mood. I had a whole playlist called "COB" just for thematic music when I was writing Chess of Blades. It can be a little dangerous at times, though; I went through an retrowave phase and was worried listening to pounding 80s synths would somehow bleed into COB's Victorian atmosphere
Ambient sound generators are also amazing. I highly recommend
MyNoise, which has a great and growing selection of ambient sounds from forests to city spaces to more abstract, tonal drones. I love the forest and church ones especially, they really transport you to another place when you're writing.
I find reading material centered around a certain time period or theme that I'm trying to replicate is pretty helpful, especially if your setting is one grounded in history. For example, while trying to capture the grittiness of the poor and downtrodden in 18th century England, I read/am reading a book that covers a lot of dark content from that period, which helps put me in the mood to write similar content.
Finally, just looking at pictures can be really helpful, too. I've got "inspiration" folders of pictures for my projects that're just filled with images that immediately evoke an atmosphere in my mind. If you have two monitors or just a wide screen, keeping one visible while writing is a very valid method.