After two experimental albums brimming with psychedelic sounds infused with blues and hard rock, UFO had to reconsider their musical direction given the limited commercial success of both records. It was just after the release of their second album, "UFO 2: Flying", and while touring Germany, that vocalist Phil Moog, drummer Andy Parker, and bassist Pete Way were struck by the talent of a young guitarist named Michael Schenker. At the time, Schenker was playing with the up-and-coming band Scorpions, who had already released their debut album, "Lonesome Crow", which had established them as one of the most promising acts in the new wave of European hard rock. In a bizarre turn of events, Michael Schenker ended up joining the British group, replacing guitarist Bernie Marsden, who was temporarily filling in for Mick Bolton, who had left the band shortly before the aforementioned tour. With this new lineup, UFO recorded their third album during the final months of 1973 and the beginning of 1974 at Morgan Studios in London, produced by Ten Years After bassist Leo Lyons. It was released in March of that year by Chrysalis Records. On this third release, the band moved away from the heavy blues and space rock of their previous two albums, focusing their sound on Schenker's guitar prowess and brilliant hard rock songs. The album contains some of the tracks that would later become UFO anthems, such as the infectious "Doctor Doctor" and the powerful "Rock Bottom". In addition to these two formidable pieces, it also featured the energetic and psychedelic "Space Child", the hard-hitting rocker "Oh My", the complex "Built For Comfort", and the rhythmic "Too Young To Know". With “Phenomenon”, UFO ushered in a new era with a more carefree and intense style, as well as being more effective and dynamic, which would bring them many years of success with albums that would go on to enrich some of the golden pages of hard rock and heavy metal.

