  Defining the musical interval of the Kirnberger kernel, or Kirn-kern, to be
one-twelfth the atom of Kirnberger, or the difference between a grad and a
schisma, its natural logarithm, k = (161/12)\ln{2}-7\ln{3}-\ln{5}, is extremely
small, k ~ 0.000000739401. Here an explanation of this coincidence is given by
showing that k = (1/6)(11\tanh^{-1}[(3/23)/11] - 21\tanh^{-1}[(3/23)/21]) ~
(2^5 5)/(3 7^2 11^2 23^3) ~ 0.000000739322.
