possibly the IIDX song blocks
made from dd_eout.dat using BLOCKS (0x02ADB0) and A-JAX 3-WAY MIX (0x2AB08)
all values hex unless otherwise stated

00-3F: full song title
40-5F: L_* - 
60-7F: T_* - Title
80-9F: unknown, usually filled with 00s
A0-BF: G_* - Genre
C0-DF: A_* - Artist
E0: unknown, changes with every song (0B in BLOCKS, 0A in A-JAX)
E8: Normal7 difficulty
E9: Hyper7 difficulty
EA: Another7 difficulty
EB: Normal14 difficulty
EC: Hyper14 difficulty
ED: Another14 difficulty
F0: unknown, changes with every song
FC-10F: unknown, usually filled with FFs
110-111: unknown, (4D04 in BLOCKS, 1E04 in A-JAX 3-WAY MIX)
114: unknown, (7F in BLOCKS, 7B in A-JAX 3-WAY MIX)
118-11F: unknown, usually filled with 30s
120-121: unknown, was C4FF in both songs
124-127: unknown, was 30386379 ("08cy") in both songs
144-164: I_* - 
164-EOB: in_* - not sure

5.1.1. is a bit different, here are the non-obvious differences (i.e.
not difficulties or references that are spelt out) that I found.
F0: 65
110-111: 6400
114: 5A
118-11F: 3161613261613030 ("1aa2aa00")
120-121: 88FF
124-127: 30313030 ("0100")

Here's gigadelic for kicks.
F0: AD
110-111: 7104
114: 29
118-11F is all 30
120-121: 0000 (odd...)
124-127: 31307465 ("10te")

and everyone's favorite TAKA repeat (that'd be V).
F0: 96
110-111: 0902
114: 50
118-11F: all 00
120-121: 88FF
124-127: 30353231 ("0521")

DXY!
E0: 04
F0: 94
110-111: 9601
114: 55
118-11F: all 30
120-121: 88FF
124-127: 30343036 ("0406")

preliminary data suggests that 124-125 is the style it first appeared in (DXY!
was 4th style, V was 5th; the only thing that this is odd about is gigadelic,
as it appeared in RED and should be 11 but is 10 instead.)

126-127, according to every song that's not A-JAX or BLOCKS, is a number.
Personally, I think it's the order in which the songs are listed in the style,
with 00 being the first. However, I have no idea what "cy" would mean. Both
songs also appeared in 10th style first, yet their first two values show "08."

MAX 300 appears as "07te," SAKURA is "08pa," PARANOIA survivor MAX is "0943,"
PF CONCERTO ANTI-ARES is "1126," Mei is "1204," SCREAM SQUAD is "1245."

Nageki no Ki is a bit different thanks to the Cardinal Gate. 124-12C spells
out "cardinal," unlike all the other songs (which have nulls in its place).
This is most likely different for pre-DistorteD games.