There is little information on Hal Saito's real name even though it is/was frequently used on album credits. Luckily,
Eric Miyashiro's homepage and this
Big Band site pretty much confirm that Kiyoshi Saito is in fact Hal Saito. Another hint might be that Hal Saito's homepage is registered under
"Kiyoshi Saito". :P
He is a sax, clarinet and flute player. There is also a oboe player "Kiyoshi Saito" credited for the Drag-on Dragoon but I'm not sure if he is the same as he might be part of the Tokyo New City Orchestra.