The following applies to most (if not all) MPU5 games:
Page 0, Option 3: Sets the volume for all sounds and music produced by the sound generator (for the reel game). Options range from loudest volume level {1} to lowest volume level {9}.
Page 0, Option 23:
Determines attract mode appearance and sounds for the bonus mode. The left digit of the Winner Paid window indicates which setting is being accessed: 1 = attract volume, 2 = attract light, 3 = attract sound. To change the setting number, turn the jackpot reset key. The setting values are displayed as follows: Winner Paid window = attract volume (right two digits); Credits window = attract light (left two digits); and Credits window = attract sound (right two digits). Press the Spin Reels button to change the value of a setting. After all the setting values have been selected, press the Change button to preview the new options for the attract mode. To save settings, exit this page by pressing the self test button.