The term 'orchestras tune to it' is referring to the OBOE, a four-letter woodwind instrument. The OBOE is a double reed instrument that produces a distinctive sound and is used in orchestras, bands, and chamber music. It is often used as the lead instrument in an orchestra, setting the pitch for the other instruments to follow. The OBOE is also used to provide a melodic line in a piece of music, and its sound is often described as being sweet and mellow.