[LeifH12345]

EQ is the wrong tool. Get iZotope RX and use spectral denoise.

Find a section of just the noise at least 0.5 seconds long, highlight it, teach it to the tool and tweak the settings so you're only reducing the noise and not damaging the music.

Since its an analog recording, if someone left the tape flips intact, there should be a section somewhere of just the noise. Failing that, there might be a quiet section of the concert where there is no other sound/applause/music to sample from.

Sometimes if a recording needs EQ, it may be best to EQ first, then do the noise reduction. Experiment. Your first results may sounds good today but may sound horrible down the road.