what musical instruments are used to define this type of music?
Acoustic instruments and wind instruments.
Progressive rock
ad some chart success, including the singles "Nights in White Satin" (the Moody Blues, 1967) and "A Whiter Shade of Pale" (Procol Harum, 1967). The Moody Blues established the popularity of symphonic rock when they recorded "Days of Future Passed" together with the London Festival Orchestra, and Procol Harum began to use a greater variety of acoustic instruments, particularly on their 1969 album "A Salty Dog". Classical influences sometimes took the form of pieces adapted from or inspired by classical works, such as Jeff Beck's "Beck's Bolero" and parts of the Nice's "Ars Longa Vita Brevis". The latter, along with such Nice tracks as "Rondo" and "America", reflect a greater interest in music that is entirely instrumental. "Sgt. Pepper's" and "Days" both represent a growing tendency towards song cycles and suites made up of multiple movements.

Focus incorporated and articulated jazz-style chords, and irregular off-beat drumming into their later Rock based Riffs, and, several bands that
which of these progressive rock groups was from america The Beatles, the Beach Boys and the Byrds, to name a few. around which year did this genre of music originate? Mid- to late 1960s. in which country did this genre of music develop? The United Kingdom and the United States.
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Progressive rock [SEP] Proto-prog and psychedelia
According to AllMusic: "Prog-rock began to emerge out of the British psychedelic scene in 1967, specifically a strain of classical/symphonic rock led by the Nice, Procol Harum, and the Moody Blues ("Days of Future Passed")." The availability of newly affordable recording equipment coincided with the rise of a London underground scene at which the psychedelic drug LSD was commonly used. Pink Floyd and Soft Machine functioned as house bands at all-night events at locations such as Middle Earth and the UFO Club, where they experimented with sound textures and long-form songs. Many psychedelic, folk rock and early progressive bands were aided by exposure from BBC Radio 1 DJ John Peel.