The defining mixing challenge in bluegrass is that every instrument has substantial midrange information — banjo, mandolin, fiddle, guitar all live primarily in the 200Hz-3kHz band. There's no synthesizer or distorted guitar to occupy the upper octaves. The work is dividing that crowded midrange into specific lanes via EQ cuts on each instrument and complementary panning to spread the spectral load across the stereo field.
The banjo is the most spectrally aggressive instrument in the genre — a high-frequency-rich attack with a substantial 200-500Hz body that can dominate the midrange if not carefully managed. The traditional approach is to pan it hard to one side, cut 3-5dB around 300Hz, and high-pass moderately at 100Hz to leave the bottom octave to bass and guitar. The result: a banjo that's clearly audible without overwhelming the rest of the mix.
The vocal in bluegrass is mixed forward and articulate, similar to country, but with even more emphasis on consonant clarity. Bluegrass vocals often sit in the 2-4kHz presence zone where the fiddle's harmonics also live, requiring careful EQ on the fiddle to avoid masking. The 4-6kHz "high lonesome" presence band where bluegrass tenor harmonies traditionally live is its own challenge: too much boost and the harmonies get harsh, too little and they disappear.