697/5000
I took a look at the audio spectrum at 528Hz using sonicvisualiser, honestly I don’t see any 528Hz, the frequency that has the highest amplitude is around 65Hz.
However I don’t think it is possible from the point of view of sound design to redo this timbre with additive synthesis.
I think it would be better to use a bank of band-pass filters and pink noise and calibrate the filters with the main frequencies, going to look at how the spectrum is composed.
Then I would add a reverb, with a good low-pass filter and a compressor.
I might even add a sine wave to reinforce the lowest / main frequency.