For those of you who want to get certain codes to work right, these four numbers (an allusion to Yuji Naka's date of birth = September 17, 1965) need to be entered first when the Sound Test is highlighted: 19, 65, 9, 17 (in that order, pressing C after each selection).
Otherwise, for example, if you attempt to input "1, 1, 2, 4" to execute the 14 continues code, you'll hear instead the Oil Ocean Zone BGM all the time. To fix that, you need to input the first four numbers in the Sound Test that not only enable the stage select code but also spell out Yuji Naka's birthday = 19, 65, 9, 17 (again, in that order and pressing C after each selection), and then you input the last four numbers, again pressing C after each selection.
~Ben