I found this one purely by accident tonight. It's "Mayonaka no Guitar" (Midnight Guitar) by Kaoru Chiga（千賀かほる）from Kagoshima Prefecture. There isn't a whole lot of information on her and what little there is seems to surround this song which was most likely her biggest hit, although she released singles from 1969 to 1978.
But "Mayonaka no Guitar" was her debut single from August 1969, and it's this lullaby-ish folk song of reassurance. If you regular readers of KKP may recall, I wrote about a guitar-themed Mood Kayo from the same decade last night by Michiya Mihashi（三橋美智也）which portrayed the protagonist as this dark knight strolling and strumming through the back streets of the city sporting a guitar like a samurai would brandish a katana. Well, you might say that "Mayonaka no Guitar" is the softer side of things. Chiga doesn't sing about having to endure a solitary musical existence; instead she invites the listener to join her in her little concert and share any miseries to resolve them. In all likelihood, Chiga isn't even strolling the dark streets. She's probably sitting on a tiny balcony while she's performing with the full moon overhead. In any case, it's a very relaxing and sway-worthy ballad, best listened to over a cup of chamomile.
"Mayonaka no Guitar" peaked at No. 4 on Oricon selling close to 450,000 records, and the song was able to win a Newcomer Prize for the 21-year-old Chiga at the Japan Record Awards, and has remained one of her representative tunes. It was written by Osamu Yoshioka（吉岡オサム）and composed by Toshio Kawamura（河村利夫）.
The soothing tune has become a standard of sorts that has been covered by a number of artists over the decades. Mizue Takada（高田みづえ）was perhaps the first singer to do so as the B-side for her 1981 single "Ai no Imagination"（愛のイマジネーション）.
Nearly 3 decades later, Hitomi Shimatani（島谷ひとみ）provided her own cover as her 30th single in 2010. Her arrangement sounds quite similar to the original. It managed to peak at No. 64.