All that can presently (May 2013) be gleaned about by internet searching is that Walter Ruel Cowles is the one-off composer of Pro Yalensi (1903).
Surfers are welcome to contribute information about this composer.
This list is arranged in chronological order and contains 1 work by Walter Ruel Cowles.
It does not claim to be complete and represents only the number of items located. Keys:ER