Cork grease is a lip balm

Lip balm

Lip balm or lip salve is a wax-like substance applied topically to the lips of the mouth to relieve chapped or dry lips, angular cheilitis, stomatitis, or cold sores. Lip balm often contains beeswax or carnauba wax, camphor, cetyl alcohol, lanolin, paraffin, and petrolatum, among other ingredients...

-like grease for woodwind and reed

Single-reed instrument

A single-reed instrument is a woodwind instrument that uses only one reed to produce sound. Examples include clarinets, saxophones, and some bagpipes. In a single-reed instrument, the reed is attached to a mouthpiece that is blown into to vibrate the reed, producing the sound...

 instruments such as saxophones, clarinets, and oboes. It is used on the corks to make putting the instrument together possible without damaging the cork and therefore possibly damaging the instrument itself. Cork grease also acts as a preservative, keeping the wooden cork moist and thick, in turn ensuring a good seal between parts of the instrument.