Its not a matter of a personal experience since everyone I ever talked to at the time easlily heard the crackling noise.
On tape it sounds like static but records faily accurately.
It probably has something to do with interference wave patterns turning on and off.

This does not happen in music since an adherence to harmonic pitch is desired. When people are not constrained by precise pitch, a general concensus of tone and pitch occurs but it seems to hover around a common pitch or harmony and not dead on intonation.

In the chanting of certain sutras I have noticed how the group collectively settles on a major third followed by a minor third out of sheer improvisation.

To make the crackling happen on purpose in a performance might indeed prove difficult. When I used to notice the crackling sound it usually developed after several minutes. While Tibetan harmonic singing can be done by an individual the crackling effect can only be achieved in a group.