: Since you included official but hard-to-find music and sound effects, I have
: some things saved on my Dropbox that would fit, all of it having been
: linked officially on HBO or b.net at one point (I couldn't tell you
: exactly where or when at this point, although a lot date themselves to
: November 7, 2013, so I'd look at the Bungie Weekly Update around that
: time).

: These include things like a clean (maybe redone?) version of the track that
: plays in the Pelican in 343 Guilty Spark , an earlier partial version of
: Difference for Darkness (then called "Rain") , what appears to
: be a pastiche of Halo 3 music , a clean version of the music from the
: Halo 3 trailer from E3 2007 , and a bunch more.

: I believe the file names are all original (except "unknown Halo 4
: music" and maybe one or two others), and I know the metadata is
: original (it has some interesting things in it too). All that's missing
: from this listing are the "lost song" from the Halo 1 OST that
: was put up for download somewhere and the copies of the Reach OST that I
: think was made free briefly, because I'm not 100% sure on the legality of
: them at this point. One or two of these may be related to Destiny rather
: than Halo, given the time frame and sound. A few files also seem to be
: corrupted; I'm not sure which ones.

: These are all hosted on my Dropbox and they've been there since I grabbed
: them. They should be available for some time but if you're archiving it's
: probably good to grab them now. Following this are links to all of them.

: ashes_piano.mp3
: battle_sketch.mp3
: Bits And Pieces.mp3
: club.mp3
: Data Hive.mp3
: fast_sketch.mp3
: ghosts_and_glass_piano.mp3
: Halo - Evolutions (Original Soundtrack) [FLAC].zip (this contains the music
: in both track and suite form for the three Halo: Evolutions stories that
: were given a motion comic adaptation and includes a file stating they are
: free to use for non-commercial purposes)
: Halo 3 E3 2007.mp3
: halo_love_theme_sketch1.mp3
: Lone Wolf.mp3
: Neon Night (partial).mp3
: ODST Theme (partial).mp3
: old_stuff.mp3
: Overture.mp3
: Prepare to Drop.mp3
: Rain (partial).mp3
: rhythm_variant_sketch.mp3
: seriously.mp3
: Steitzer.zip (this contains a bunch of alternate and unused announcer lines
: for Reach, some of which may hint at later gametypes or concepts like
: Power Slayer and Ricochet)
: string_sketch.mp3
: Super_in.mp3
: Super_out.mp3
: The Rookie.mp3
: Traffic Jam (partial).mp3
: tron.mp3
: unknown Halo 4 music.ogg
: what.mp3

: In going over these, I checked that text file for the Halo: Evolutions
: tracks, it refers to this Soundcloud page , belonging to Paul Lipson, the
: person that made the music in the first place. He also has selected clips
: from the Halo: Anniversary soundtrack on there, and some bits from other
: Microsoft and Pyramind projects.

: I hope these are helpful or entertaining!

Is there a name change feature? I prefer my current username "UncookedMoa" lol.

As for the tracks you've provided, these were released for free officially at some point, indeed. They do deserve to be archived, but I believe you're misinformed in places. All the sketches are still on Bungie.net and it's stated that they're all for CE. As such "string_sketch" is Halo CE, not Halo 3. It's officially named "Familiar Themes." It's an earlier version and later became "Enough Dead Heroes" in the final game, and OST. The later portion of it likely ended up being reused in Halo 3 for "No More Dead Heroes" and "Wake Me When You Need Me." Club, what, tron and old stuff are also sketches. They're not redone. "Old Stuff" is either identical, or an older version of the one in the game, since it's a sketch.

I also believe the ODST tracks are identical to their OST counterparts. For example, let's take "Prepare to Drop". It's the same as the ending portion of "Finale" in the ODST OST. As for "Rain" - that is the official name of that portion of Deference For Darkness (not "difference"). Deference For Darkness is a suite of tracks. Rain is the name of that beginning piano portion of it. ODST Theme is essentially being the E3 2009 version of the track, which was more or less just a portion of "Finale."

Halo 3 E3 2007 is interesting, though. I also have this, and it's more or less a remix of One Final Effort.

Reach is the most interesting stuff. Ashes piano and Ghosts and Glass piano are effectively stems of the official tracks featuring only the piano portions. Already had these though. Lone Wolf is the VGA trailer version, but sounds more or less identical to that portion of Winter Contingency. I have two additional promotional Reach tracks aside from those you've provided. These would be "Lone Wolf Ringtone" (shorter - meant for a looping ringtone) and "Noble Map Pack Trailer Music" (A remix featuring all Bungie's Halo themes).

As for "unknown Halo 4 music" - It's definitely a portion of Arrival, but it's not identical. Sounds like a lower quality, muted version of the full thing, as if it's a background track, or a teaser of some sort. I wasn't following Halo 4 development enough to spot that, so I don't know the context for it.