Mo. Rev. Stat. § 509.380
All motions may be heard and other acts or proceedings, except trials upon the merits, may be done or conducted by a judge in chambers, without the attendance of the clerk or other court officials and at any place either within or without the county; but no hearing, other than one ex parte, shall be conducted outside the county without the consent of all parties affected thereby.
(L. 1943 p. 353 § 70)