This is a song that I often heard on all those old music retrospectives such as "19XX", and considering what was being played in Japan during that decade of the 70s, I thought it was just one of the more cheerfully unusual tunes that I had ever heard.
SHOGUN was a band that was first brought together through a conglomeration of studio musicians including guitarist Fujimal Yoshino （芳野藤丸）which had released the album, "Yellow Magic" under the band name of One Line Band. A majority of that grouping stayed together to become SHOGUN. As for how the name came about, a staffer for the Nippon Television Music Corporation had gone to America for a vacation and at a US airport, he saw a ton of James Clavell's "Shogun" novels stacked up somewhere. So when he returned to Japan, he made the suggestion to his junior colleague Noriko Iida （飯田則子）who had taken an interest in Yoshino's group; Iida had always dreamed of a Japanese band whose name could be understood overseas, and with her senior's suggestion, that was that for this particular group of musicians.
The debut song for the new band of SHOGUN was "Otokotachi no Melody" (Melody of Men) which became the theme song for an action-comedy titled "Oretachi wa Tenshi da!"（俺たちは天使だ！...We Guys Are Angels!）about a group of motley detectives and their agency. Released in April 1979, it was written by Makoto Kitajo （喜多條忠）and composed by then-member Casey Rankin. Starting with a blast of anthemic rock guitar, the song quickly transitions into a comical country-style melody, perhaps reflecting how the TV show progressed, and one of the things I remember from the song was the English that popped up now and then such as "Pick up your head, throw away your blues". I thought it was more suited to the hills of Kentucky than the skyscrapers of Tokyo.
The song became a big hit for the band which, according to J-Wiki, scored over half a million records (although entamedata shows a far more modest number) in sales and became the 64th-ranked song of the year. However, even more fame was to come in a couple of singles with "Bad City", another catchy detective show theme.