In the Japanese version, the menu voice is named 'Memo', instead of 'Comment'. The Japanese version also shows 4 notes on each page, instead of 2 notes.
Believing that a female lead would not be received well, Capcom added in a dog partner that could attack enemies. After this change, they further designed the gameplay around this partner mechanic.
Rather than streaming audio files, the music for Haunting Ground was generated by using the PS2's built-in sounds. This way, the composers could easily change the tempo of the music during gameplay.