This is the one I am not sure how to do....


What you described sounds to me like most of the bass and treble frequencies got lost in the recording. This would be typical of bootleg recordings; bass gets absorbed by a mass of bodies, and treble can get absorbed by eg, the material that a pocket is made of, the microphone's frequency response etc.

But you also mentioned needing to reduce the bass. This bass that needs reducing, is it sub-bass range? (ie 30-80Hz, wouldn't get absorbed so much by a mass of people), or is it higher? If it's higher, it could be room resonance - that gives a boomy appearance to the sound despite there not being any real bass in the music. (Assuming that the room is rectangular, there could be up to 3 prominent resonances that should be fairly easy to reduce).

(In fact, thinking about it more, it's probable that the microphone wouldn't pick up much sub-bass anyway..)

Whatever,
A decent EQ, HW or SW should be able to make it much more listenable (31 band graphic, or a sweep EQ (more commonly, but incorrectly called a parametric EQ, such as the empeg's EQ))

Got a sample?