Tanaka composed two vocal themes for this game, which appear on this single:
http://vgmdb.net/album/9673.
Perhaps some of the confusion is because both Tanaka and Tada are listed under the generic header "music" (音楽) in the game:
http://www.geocities.jp/bgrtype/gsl/...rademarch.html. Both the game credits and this album do specify that Tada was wholly responsible for the BGM.