Angelus: Akuma no Fukuin (PC-88)

Angelus: Akuma no Fukuin
Developer: Enix Publisher: Enix Platform: PC-88 Released in JP: July 1988 This game has a hidden sound test.

After two completely unrelated individuals obtained a mysterious sickness, and a third one started developing those same symptoms in front of him, the London Post reporter Brian Paul is sent to investigate the circumstances alongside his girlfriend Eris, leading them to a world of cults and evil gods.

Sound Test

To access the sound test menu, boot the game while holding T + A + G + U + C + H + I + @ + K + O. Due to the number of keys that need to be pressed, programs such as Key Input Helper for M88 can be used to assist the code's input.

Additionally, a small dialogue is seen before the sound test properly begins:

エイミ	アンジェラスの音楽でーす！	Amy	It's the music from Angelus!
美春	うわあーい！早く聴きたーい！	Miharu	Wow! Can't wait to hear it!

(Source: ayachidaichi)