Picture of Side A of the vinyl, from this Yahoo auction (
http://page15.auctions.yahoo.co.jp/jp/auction/t218568681):

"Music By FUMIO"
Credits from this Yahoo auction (
http://page14.auctions.yahoo.co.jp/jp/auction/s307033904),
All composed & arrangement by Fumio Miyashita
musicians:
synthesizer: Fumio Miyashita
percussion: Yujin Harada
bass: Kei Ishikawa
key bord: Ken Mishiro
guitar: Chitose Shibata
song by Sumiko Yamagata (B-5) やまがたすみこ
The Arion comics ran from March 1979 to September 1984. So this LP from 1983 actually predates Hisaishi's music (the anime film adaptation was in 1986, also the year His' score was released). So the only way to hear HisSynth is on the Digital Trip 1800 Series ARION Synthesizer Fantasy (
http://forums.ffshrine.org/f91/only-old-anime-osts-bgm-einachi-67259/206.html#post2344824) album (Link is dead. I have downloaded it though, so I'll re-upload it if I have time). Or the soundtrack/image album since back then His' scores were partly performed by studio orchestras :'D