When adding treble or bass, be sure the controls are doing what you expect them to. If you don't obtain an appreciable improvement, move on to a different frequency. Remember, a lot of boost at the extreme low end can route excessive infrasonic energy to the loudspeakers, which could damage them. Similarly, too much ultrasonic content can damage tweeters and overload the tape deck. The chart below lists some common instruments with frequencies at which boost or cut can be effectively applied to cure various problems or obtain certain effects.
Indicated frequencies are necessarily approximate, as no two instruments sound exactly alike.
The Comments column gives cautions or observations based on experience. They should be taken as guidelines rather than prescriptions, because every situation is different and every recordist has his own sonic goals. A few general hints may contribute to the effective use of equalization. Leave some room for contrast. Critical listening tends to numb one's senses after a while, especially if you listen at high volume levels.