Dialogue and sound effects spilling out like a radio drama you accidentally tuned into. Forest Flying Circus is a drama CD from the Forest visual novel series on PC, released back in 2004. The tracks are numbered rather than named, which gives the whole thing this mysterious, unpackaged feel.
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Track 1 sets the stage. Track 4 hits different partway through. This is deep visual novel territory, the kind of thing fans mail-ordered from Japan through specialty shops. Mid-2000s PC doujin culture at its most niche. You probably won't stumble onto this by accident.
But if you're into the Forest series and want the complete picture, this is the missing piece sitting in someone's collection gathering dust.