Yamaha YMF795 Manual page 36

Using a resister R3 can obtain the following frequency characteristic.
Gain1= (R2+R3) /R1. Gain2=R3/R1.
Filter cutoff frequency of f1 and f2 is:
f1=1/ (2π×R1×C1).
f2=1/ (2π×R2×C2).
Gain
Gain1
Gain1-3dB
Gain2
C1 R1
EQ2
EQ1
FM
VOL
VREF
f1
C2
R3
R2
-
+
f2
-36-
YMF795
EQ3
Freq