He debuted as a member of GS's The Baron. The Baron was formed in February 1967 as a back band of 尾藤イサオ (Isao Bito). Their debut was in June 1st 1969, a single "Blue, Lonsome, Dream" in the name of "ジュリーとバロン" (Julie and Barons) with girls singer 鍵山珠里 (Juri Kagiyama). Their 2nd single released in November 5, 1970 which was under the name of The Baron.
Upon the start of "Stage 101" broadcasting, He joined "Young 101" formed for the program in 1970. Debuted from Toshiba Express as a duo group "ワカとヒロ "Waka to Hiro (Waka & Hiro)" formed with 若子内 悦郎 (Etsuro Wakakonai).
His name was 河内広明 Hiroaki Kawachi at that time, which ultimately remained due to the withdrawal of other members.
Released several records on the alias Hiro Serizawa (芹澤廣 and 芹澤ヒロ) before beginning to use his full name as a composer.