If I'm just flying against AI, I'll usually pop in some music of various kinds. Metal, Rock, whatever I'm in the mood for. Maybe some 80s Punk, or something like that to really get me going. But if I'm flying People vs People, I'm usually listening to the engine and the sounds of my ShVAK 20mm Cannon or twin Berezin UBS 12.7 MGs... and if I'm not flying a Yak-3, I'm listening to my early quadruple 7.62 ShKAS MGs on my I-16 type 10 while fighting in the skies of Spain, and downing the latest victim in an Italian-made Fiat Cr. 32 Biplane. ;)