Polyphony and monophony in instruments harpejji and the Chapman stick). Multiphonics can be used with many regular wind instruments to produce two or more notes at once, although this is considered an extended technique. Explicitly polyphonic wind instruments are relatively rare, but do exist. The standard harmonica can easily produce several notes at once. Multichambered ocarinas are manufactured in a number of varieties, including double, triple, and quadruple ocarinas, which use multiple chambers to extend the ocarina's otherwise limited range, but also enable the musician to play more than one note simultaneously. Harmonic ocarinas are specifically designed for polyphony, and in these instruments the range
Owned-and-operated television stations in the United States Westinghouse to trade its NBC-affiliated Philadelphia cluster of KYW-AM (1060) and WPTZ-TV (channel 3) to NBC in exchange for WTAM-AM-FM and WNBK-TV in Cleveland. Westinghouse only agreed to the trade after NBC threatened not only to yank its programming from WPTZ, but also Westinghouse-owned WBZ-TV (channel 4) in Boston. NBC changed the callsigns of the Philadelphia stations to WRCV-AM-TV, while Westinghouse changed the Cleveland stations' callsigns to KYW-AM-FM-TV. NBC's then-ownership of Philadelphia's channel 3 was cited by CBS when it purchased its then-affiliate WCAU-TV in 1958, despite FCC rules at the time barring companies from owning stations with overlapping signals,