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 fourth-ranked Philadelphia housed CBS-owned WCAU-TV (channel 10) and NBC-owned WRCV-TV (channel 3, now KYW-TV), a station which NBC had acquired two years earlier through a trade with Westinghouse Broadcasting in return for NBC's television and radio stations in Cleveland. The FCC reversed the trade in 1965 and NBC regained control of the Cleveland television station, which is today known as WKYC. Each network owned stations in other markets where the other networks did not: in addition to Cleveland, these were ABC's KGO-TV (channel 7) in San Francisco and WXYZ-TV (channel 7) in Detroit, NBC's WRC-TV (channel 4) in Washington, D.C.,