Yes


Nope.  No extra sound in AOROM at all.  AOROM is actually very, very, very simplistic and bare-bones.  Many of the games that use it are coded by insane madmen and do very crafty things to push maximum power out of the minimum a mapper can provide (you mention battletoads, which is an infamous example of this -- that game pulls off an insane amount of really cool tricks).


Not going to happen.  All the kickdrum/punch/etc sound effects in Battletoads are streamed PCM (writes to $4011 at timed intervals).  In order to play this sound effect you need to dedicate a VERY large portion of in game CPU time into LDAing sample data and STAing it to $4011 every few cycles.  It's tricky and extremely time consuming -- in fact, you can't really do much else while you're doing it.

Ever notice how everything in game stops when it plays those sound effects in game?  And during the title sequence, you can notice the text drawing and things get choppier when the drums are playing -- and the drums in the title screen cut out completely for parts where there's too much on-screen action going on.


$4011 is part of the DMC, but it's not the "usual" DMC.  Most DMC sound effects are fetched and streamed automatically by the DMC unit, so all it takes is the sound effect stored in ROM somwhere, a few register writes, and then the hardware takes care of the rest.  $4011 streaming has to be done completely in software -- no hardware support.


- EDIT -

I suppose you could always convert the streamed PCM to the DMC format and play it the "normal" way.  Then you could probably get it to work in Mario/Zelda.  It would only be an approximation of the original sound, though.  Probably wouldn't sound as good.

I'm pretty sure there are wav->dmc conversion utilities.  If you can get a wav recording of sound effect (without other sound channels playing -- which is probably relatively easy to do during the pause screen in Battletoads), save it as an 8-bit mono .wav file and run it through a conversion util.  I don't think there are any on this site, but you can check 2a03.org or nesdev.parodius.com for one (2a03.org would be my first target).

Keep in mind, though, with this method there will be significant quality loss.  You may be better off taking a kickdrum sound from another game.  Konami had some pretty good ones used in the CV series and TMNT1.  If you go this route you won't have to mess with conversions, and the samples themselves quite possibly have already been ripped from the game (again, I'd check 2a03.org for them -- maybe even post on the forums there about it).


Nothing particularly special about it.  Only thing to mention is it doesn't allow swapping at $C000-FFFF with the standard setup (which I'm sure DW uses) -- and that DMC samples must lie within that range.  Which means you'll have to clear out or move a significant portion of code/data from that bank to make room for the sample data.


EDIT:

Also should mention this.

It's been semi-recently discovered that the DMC can interfere with serial register reads -- notably $4016 (joypad) and $2007 (PPU reading).  The DMC can insert 'dummy' reads from these addresses if the DMA occurs while the game is reading from them.  This can mess up your joypad data or mess up the data you're reading from the PPU.

If you add the DMC to a game which does not use it, be sure to do the following:

1)  Redo the joypad reading routine so that it strobes and reads data multiple times (at least twice).  Generally I think games keep reading data until they get 2 sets of buttons that match.

2)  Make sure the DMC isn't playing during $2007 reads.  I doubt Dragon Warrior reads from $2007, so you probably don't have to worry about this -- but you never know.

Emulators will not catch this, but things like the PowerPak will exhibit very strange quirks if you fail to do this (like the player seemingly randomly walking on his own due to false button presses caused by disrupted joypad reads)


EDIT2 -

Relevent information:

http://nesdev.parodius.com/bbs/viewtopic.php?t=4116

Yes.  I think Konami uses the noise for its snare drums in many games (CV2 comes to mind).


It all depends on the music driver.  Since you'll be adding this stuff to a game which doesn't already support it, you'll have to write your own driver, which means you can design the format any way you want.  It might be easier to have a single byte represent a specific sound effect.. like maybe:


Which would wait 2 measures, then play a kickdrum every beat and a snare every odd beat (see it?).

The length of whole/half/quarter notes will need to be translated into a number of frames -- which you'll have to examine the game's existing music driver to figure out how it figures that out so that you can match its tempo.

As for actually playing these...

DMC is pretty easy, just set up the regs at $4010-4013 to have it point to your sample data and stuff... then start it up with $4015.

Noise is bit trickier.  Noise sound effects will often require attention for several frames.  Like you'll have to set the regs to something one frame, then set them to something else a few frames down the line, then to something else, etc.  This isn't terribly difficult to do.

Noise comes down to three basic parts:
- mode:   short (bzzz) or long (shhhh)
- freq:   the pitch, low or high (16 possible pitches for noise)
- volume: 16 possible output volumes:  0 (silence) - $F (full)

Creating a good sound effect will require pitch and volume changes at a somewhat rapid rate.  This is just an example, but say you want to do the following for a sound effect:

- Freq 5, vol 7  for 5 frames
- Freq 7, vol 6  for 2 frames
- Freq 8, vol 3  for 9 frames
- Freq 8, vol 0 (sound effect done)

You could store this like so:


You'd just need to keep a counter which counts down every frame to know when to perform the next part of the sound effect.  And you'd need to keep a pointer of sorts to know where in the sound effect you currently are, so that when the down counter expires you know which byte to apply next.  Applying the volume and freq changes are as simple as [properly] copying those numbers to the noise regs.

There's also a decay unit on the noise if you want rapid (faster than 1 frame) volume changes.  But that'll probably be unnecessary and would require a more complicated sound effect format.

Music driver stuff is fun, but a lot of work.  Getting it to work alongside an existing music driver is an even bigger challenge.  You might want to consider gutting the game's original music/sound effect system and writing your own.  In the long run it might be simpler -- or not.  It's hard to say.




Fortunately most games have a specific routine for polling the joypad reg.  So you just have to find that one routine and change it and you should be good to go.


Likewise.  I love music driver stuff.  If you need further theories/explanations/whathaveyou, don't be shy. ^^