1. A humidifier comprising: an open top receptacle containing a quantity of water therein, said receptacle having an outwardly extending flange defining the open top thereof, an electrical heating unit positioned within a rigid outer tube and mounted transversely of said receptacle to said flanges by clamp members encircling the ends of said outer tube, and a plurality of wick means spaced from each other engaging said heating unit, said wick means having their free ends immersed in said water to a depth adjacent the bottom portion of said receptacle and conveying to said heating unit by capillary action a quantity of water for evaporation, said heater having exposed portions between said wick means whereby the surrounding air is heated and moistened by thermo-convection air currents moving through and around said wick means.

8. In combination with a muscial instrument provided with an enclosed space such as a piano having opposed surfaces disposed below a structural component, a dehumidifier in the form of an elongated rigid tubular heating unit mounted between the opposing surfaces, a humidifier supported below the structural component and below the dehumidifier, and a humidistat mounted on the dehumidifier and controlling the humidifier and dehumidifier to maintain a desired relative humidity within the instrument, said humidifier including an open-topped receptacle disposed vertically below the dehumidifier, a heating unit extending across the top of the receptacle and being rigidly supported therefrom, said receptacle and heating unit mounted thereon having a lengTh substantially less than the dehumidifier, wick members supported from the heating unit on the receptacle and depending into the receptacle, said receptacle including a quantity of water therein engaging the lower ends of the wick members, means on said heating unit on the receptacle to space the wick members apart to expose a substantial portion of the heating unit.