I have been running tests all evening investigating the effect of various changes to subcode data and the production of rare (/???) monsters in Monster Rancher 1. As it is now extremely late and I don't know how to make tables in HTML yet (that's tomorrow's project so I can show you my results), I'll give the brief synopsis:
The values of PMin and PSec in [Entry 2], or total minutes and seconds of the album, are the key. PFrame doesn't seem to matter, and PLBA is a calculated value PLBA=(PMin*60+PSec)*75+PFrame-150. The same calculation applies to ALBA, AMin, ASec and AFrame, but they seem to have no correlation or use in generating MR1 monsters.

Hopefully soon I'll have my results of tinkering with Nirvana Nevermind (and actually getting a Nya from the BMG version of the CD) up so you all can see.
The cause is not dead, it was just in hibernation. Let's wake it up.

Next on the agenda: hunt down that missing Henger.

Disclaimer: this information is currently limited to MR1, as I have not had an opportunity to progress in MR2 far enough to get any rare monsters.

Do you have a DexDrive? If you do, I could e-mail you the save that I found. The trainer's name is AAAAAA, I think, and all monsters are unlocked. I also played it long enough to upgrade the house and stable, and raised a Flare Death. It has some rare monsters saved on it as well.

This offer goes to anyone who would like me to send them the file. Just email me to let me know, or give your email address, and I'll send it to you.

Okay, I managed to waste yesterday afternoon investigating the effect of modifications of the sub-code information on the monsters created in Monster Rancher 1.
Disclaimer: The following information is not to be held as an exact rule as to how the game interprets this information, but merely my observation with a very small sample. Due to my lack of experience with Monster Rancher 2, these results probably will not translate very well over to that game.

My observations make use of the Karaoke (Nya/???) MR1 rare monster (posted as the Swimmer MR2 rare on this site) and the sub-code data extracted from my brother's copy of Nirvana Nevermind, BMG version (which under normal circumstances gives the Stoner Hare/Golem monster in MR1).
I have also used the Seuki Suezo information to assist in a few observations, as well as the Ramone's Mondo Bizzarro and Chipmunks Christmas subcodes that have been posted by Lisa in other threads.

Testing equipment used: Monster Rancher 1 for PSX (US version), Playstation 9001 series (my brothers, since my older model refuses to read CD-RW discs as valid input), a small (1.5MB) image file collected with CloneCD to minimize write times, a CD-RW drive, CloneCD v.2, a CD-RW disc (to save costs. It can be erased after each use and re-written with a new sub-code), and Norton File Compare to check for differences between sub-code (CCD) files.
I used CloneCD's erase CD function before each write to remove the previous data.

In regards to rares:
The main elements that seem to be used by the shrine in determining the monster are the PMin, PSec, and PFrame values in the [Entry 2] part (which has Point=0xa2). These values appear to relate to the full length of the CD.
The entries after this are for the actual tracks (I used a music CD with 12 audio tracks, Entry 3 through 14, Point=0x01 to 0x0c). In each of these Entry's, the PMin, PSec, and PFrame values are the start time for the track.
The PLBA value is calculated according to the following formula:
PLBA = ( PMin * 60 + PSec ) * 75 + PFrame - 150
Or in english terms: the number of frames the tracks use starting after the first 2 seconds, where 75 frames = 1 second.

I tested varying the PMin, PSec, PFrame, and PLBA values in [Entry 2], TocEntries values (in the [Disc] section at the top), and the number of [Entry] tracks included. My results are in the charts below:

1. total time modification (PMin

PSec

PFrame)

PMin	PSec	PFrame	PLBA	Name	Main	Sub	Lif	Pow	Def	Ski	Spd	Int	total
42	23	0	190575	Stoner	Hare	Golem	114	191	90	98	110	126	729
42	23	70	190645	Stoner	Hare	Golem	114	191	90	98	110	126	729	Hare/Golem
42	37	74	191699	Stoner	Hare	Golem	113	189	91	95	111	140	739	change in stats
42	38	0	191700	Karaoke	Nya	???	152	132	131	155	125	185	880
42	38	70	191770	Karaoke	Nya	???	152	132	131	155	125	185	880	same as Swimmer.CCD
42	38	74	191774	Karaoke	Nya	???	152	132	131	155	125	185	880
42	39	0	191775	Stoner	Hare	Golem	114	191	103	102	107	142	759	change in stats
43	38	70	196270	Rocky	Suezo	Golem	108	182	115	85	99	151	740
59	23	0	267075	Stoner	Hare	Golem	114	191	90	98	110	126	729	Nevermind BMG.CCD

2. absolute time modification (Nevermind BMG.CCD was used with A values taken from Swimmer.CCD)

AMin

ASec

AFrame

ALBA

Name

Main

Sub

Lif

Pow

Def

Ski

Spd

Int

total

10

27

11

46886

Stoner

Hare

Golem

114

191

90

98

110

126

729

Amin/Asec/Aframe/ALBA

3. PLBA modification without respect to time

PMin	PSec	PFrame	PLBA	Name	Main	Sub	Lif	Pow	Def	Ski	Spd	Int	total
59	23	0	267076	Stoner	Hare	Golem	114	191	90	98	110	126	729
59	23	0	191770	no read			0	0	0	0	0	0	0
42	38	70	267075	Karaoke	Nya	???	152	132	131	155	125	185	880

4. TocEntries modification

PMin	PSec	PFrame	PLBA	Name	Main	Sub	Lif	Pow	Def	Ski	Spd	Int	total	TocEntries
59	23	0	267075	Dino	Dino	Dino	118	122	91	144	102	103	680	4
59	23	0	190575	Warrior	Gali	Golem	124	181	120	78	90	136	729	5
59	23	0	267075	Fencer	Jell	Golem	124	161	120	98	80	136	719	6
59	23	0	267075	Rock Worm	Worm	Golem	144	181	100	98	80	126	729	7
59	23	0	267075	Toto	Tiger	Golem	124	161	90	108	110	126	719	8
59	23	0	267075	Rock Bush	Plant	Golem	154	161	120	98	90	126	749	9
59	23	0	267075	Trident	Naga	Golem	124	191	120	108	90	96	729	10
59	23	0	267075	Obelisk	Monol	Golem	124	181	130	78	90	126	729	11
59	23	0	267075	Stoner	Hare	Golem	114	191	90	98	110	126	729	12
59	23	0	267075	Anki	Dino	Golem	124	191	100	88	90	106	699	13
59	23	0	267075	Rocky	Suezo	Golem	114	181	100	98	90	136	719	14
59	23	0	267075	Stoner	Hare	Golem	114	191	90	98	110	126	729	15
59	23	0	267075	Anki	Dino	Golem	124	191	100	88	90	106	699	16**
42	38	70	191770	Karaoke	Nya	???	152	132	131	155	125	185	880	14
42	38	70	191770	Karaoke	Nya	???	152	132	131	155	125	185	880	15

** Because the CD only has 15 entries normally, I fabricated an Entry 15 to bring the TocEntries count up to 16. I gave it Point=0x0d, PMin 40, PSec 0, PFrame 0, PLBA 179850 to make it seem realistic. Everything else was copied from Entry 14.

From the 28 variations of subcode tested above, I have drawn the following conclusions:
1. This seems to determine part of what monster is created. When trying to unlock the rare, I only needed to be exact to the PMin and PSec, the PFrame value did not seem to matter (both extremes of 0 and 74 were tested).
It took a variation of the PMin value to change the monster main type, values close to those of the rare gave a change in stats.
Some investigation of the variations on the Ramone's CD subcode will need to be tested to determine how much variation will be needed to cause a change in monster subtype and stats.
2. Modification of the AMin, ASec, AFrame and ALBA values has no effect on the monster created.
3. An increase in this value does not seem to affect the monster, but trying a much smaller value than should exist resulted in the CD not being read at the shrine.
4. There must always be at least a track at Point=0x01. Removal of this will result in CloneCD not writing to the disc.
Varying the TocEntries value and adding/removing Entry # from the .CCD file causes a change to the monster main type, each with a seemingly standard stat total and range.
Having only 1 actual track (TocEntries=4) causes a purebreed Dino, everything else was a Golem subtype.
(though it seems it may only be necessary to change the TocEntries value, I lowered this by one to 14 from 15, but left Entry 14 in place and got the same result as when I removed Entry 14. However if the value is increased, it is most likely necessary to fabricate a new Entry section).

The monster subtype and stat range could be tied to the PMin and PSec values in Entry 2 and/or 3 (I did not investigate changes in Entry 3, only Entry 2 so far), while the main type might be related to the TocEntries value.

The rare monsters most likely have a set value for all stats, as I saw no variation in this.
Values affecting monster subtype and changes in values for skills are as of yet undetermined for certain (PMin and PSec seem to have some effect), but the following are ruled out: AMin, ASec, AFrame, ALBA, and Control (this last was from observation of some other data than the Nirvana CD).
These warrant further investigation, perhaps from the subcodes from the two pressings of the Ramones: Mondo Bizarro would help, as these show variation in subtype and stats.

It might be possible to manufacture a rare from a different pressing of a CD that should give one, provided the full length can be learned or guessed (minutes and seconds should be all that's needed, MR1 doesn't seem to care about frames for this, which would make this almost impossible).

So if anyone out there has a Beck: Mellow Gold that doesn't give the rare, but you have a good guess at what the actual length of the album should be, feel free to share.

Sorry for the insanely long post, but I just wanted to try sharing research.

Sorry, WHTJunior, I don't have a Dex drive, but thanks for the offer. I also normally don't have that much free time (with the occasional rare exception, see above), so I think I'm going to refrain from any MR2 testing right now.
Hopefully I've given some other people with more resources some leads to start on that though.

Good luck and happy ranching. When I get the opportunity, I plan to continue the above experiment, but it might be a while.

Thanks for the hard work!

I must say, I'm quite impressed. I will have to
add this research to my own (when I get a
chance).

--Cats

Here's the results of a brief night's work on Lisa's Mum/Mew version of Beck: Mellow Gold.

Beck
Pmin	Psec	Pframe	PLBA	Name	Main	Sub	Lif	Pow	Def	Ski	Spd	Int	total
47	38	60	214260	Ray	Suezo	Plant	152	123	116	121	121	168	801
47	39	60	214260	Ray	Suezo	Plant	158	129	114	138	109	169	817
47	39	60	214335	Ray	Suezo	Plant	158	129	114	138	109	169	817
47	40	60	214410	???	???	???							0

These are purely Monster Rancher 1 results. The ??? for the monster on that last one is because I don't have committe approval for it yet, and fyi, the only monster I have not unlocked yet is the Henger.
The subcode is posted in the Laboratory under the Monster Rancher 1 Requested CDs section.
Try at your own risk and amusement at what this fool has brought.

Good luck and happy ranching.

Prepare to be more impressed:

Enigma's ??? CD turns out to be a Magnet!

LIF	POW	DEF	SKI	SPD	INT
100	127	94	166	160	126

Try it in MR2!!!!!

Oh, I see, Mum Mew again.....
This really is great news! Thanks for all the hard work!

If anyone knows a gameshark code that unlocks all monsters in Monster Rancher 2, I'd be willing to try for the Moo/???.
I have a "Gold Finger" device which claims to have Gameshark and mod-chip functionality for my playstation, but it only works on my old PSX (1001) series, which doesn't read CD-RW's, so I'm thinking if I can start a new game with everything unlocked, save it, and use it on my brother's 9001 series PSX which can read CD-RW's so I can continue the hunt.
Otherwise, if such a code doesn't exist, I'll have to postpone such research until I can find a Dex Drive for sale or unlock everything myself, which might not be for a few more months.
I know what you're saying, that unlocking the monsters is half the fun of the game, and I agree with that, which is why I don't intend to actually play a game like that from the beginning. I just want a way to continue this line of research, and that's the only way I can see it happening anytime soon, unless someone else takes up the challenge to determine what makes a Monster Rancher 2 rare.

Whatever I find first, if I make any further headway on this, I'll keep you posted.

Happy ranching.

By the way, I finally unlocked the Henger in Monster Rancher, so I was finally able to see the fruits of my labor. ^_^

Happy ranching.

The codes offer three options: one is that you can have them all unlocked (no actual monsters in your possesion, you just now have permission), or alter a frozen monster to be anything you want (catch is that inside it is still the original monster in terms of statgain & preferences), or the DNA capsule option, which is probably your best shot. Look in the MR2 archive in the Gameshark codes section. I think there's a guide to which DNA capsule does what in the Items section.

Thanks, I got the Gameshark code to work as I was hoping, preauthorizing me to get all the monsters (no more "you can't get that monster yet" messages from the shrine ^_^), so I should be able to continue this line of research into Monster Rancher 2 as time allows.

On a side note, a bit of irony that you might enjoy. I acquired a copy of Beck's Mellow Gold that gives the Henger in MR 1, and the Mum Mew in MR 2. I copied out the subcode data, and it is IDENTICAL to the modified one I made off of Lisa's copy. Down to the PFrame value. 47 min, 40 sec, 60 frames.

I am going to start my hunt with the same place I did last time, the Nirvana Nevermind disc, so when I get to the Mellow Gold disc I'll know where to start.

Happy ranching.