Unless otherwise agreed a product of the mind, in the production of which several persons are jointly concerned, is owned by them as follows:

(1)    If the product is single, in equal proportions; or

(2)    If it is not single, in the proportion to the contribution of each.

Source: CivC 1877, § 571; CL 1887, § 3194; RCivC 1903, § 887; RC 1919, § 485; SDC 1939, § 51.0805.