Original list (left most column) by Shwiffer. Middle column = decision to keep original music, change it for something else, or replace with ambient sounds from MizterMoonshine's mod. Right most column = what replaces what, considering LordBraathen's original Sound folder.

song_5strong | Launcher, the Daggerfall theme.MUSIC CHANGEReplaces song_12, replaced by song_overlong
song_02 | Overworld, clear day and cloudy.AMBIENT DAYReplaces song_20
song_03 | Overworld, clear day and cloudy.AMBIENT DAYCut
song_04 | Dungeons. MUSIC CHANGECut, replaced by song_10
song_05 | Dungeons.MUSIC KEEP
song_06 | Palace theme.MUSIC CHANGEReplaces song_gpalac, replaced by song_gpalac 
song_07 | Dungeons.MUSIC KEEP
song_08 | Overworld, rain.MUSIC KEEP
song_09 | Sneaking.AMBIENT DUNGEONCut (not currently used)
song_10 | Overworld, night.AMBIENT NIGHTReplaces song_04
song_11 | Overworld night and in court.MUSIC CHANGECut, replaced by song_dag_12
song_12 | Overworld, cloudy and foggy.MUSIC CHANGEReplaces song_snowing, replaced by song_5strong
song_13 | Overworld, foggy.MUSIC CHANGECut, replaced by song_gsnow__b
song_15 | Dungeons.MUSIC CHANGECut, replaced by song_16 (not previously used)
song_16 | Sneaking.AMBIENT DUNGEONReplaces song_15
song_18 | Overworld, night.AMBIENT NIGHTCut
song_20 | Overworld, snowing.MUSIC CHANGECut, replaced by song_02
song_21 | Overworld, night. Normally a duplicated song_10.AMBIENT NIGHTReplaces song_gsnow__b
song_22 | Overworld, clear day and cloudy.AMBIENT DAYReplaces song_29
song_23 | General interiors including houses and most guild interiors.AMBIENT INTERIORReplaces song_ggood
song_25 | Sneaking.AMBIENT DUNGEONReplaces song_oversnow 
song_28 | Dungeons.MUSIC KEEP
song_29 | Overworld, cloudy and foggy.MUSIC CHANGECut, replaced by song_22
song_30 | Sneaking.AMBIENT DUNGEOUNCut (not currently used) (potential for boss fight music)
song_dungeon | Dungeons, namely Privateer's Hold and Scourg Barrow.MUSIC KEEP
song_dungeon5 | Dungeons.MUSIC CHANGECut, replaced by song_d2 (not previously used)
song_dungeon6 | Dungeons.MUSIC KEEP
song_dungeon7 | Dungeons.MUSIC KEEP
song_dungeon8 | Dungeons.MUSIC CHANGEReplaces song_gbad, replaced by song_d3 (not previously used)
song_dungeon9 | Dungeons.MUSIC KEEP
song_folk1 | Taverns.MUSIC KEEP
song_folk2 | Taverns.AMBIENT TAVERNCut
song_folk3 | Taverns.MUSIC KEEP
song_gbad | Temples.MUSIC CHANGECut, replaced by song_dungeon8
song_gcurse | Overworld, night. Seems to play in context of ruins.AMBIENT NIGHTCut
song_gday___d | Overworld, clear day and cloudy.AMBIENT DAYCut
song_gdngn10| Dungeons.MUSIC KEEP
song_gdngn11| Dungeons.MUSIC CHANGECut, replaced by song_d5 (not previously used)
song_gdungn4 | Dungeons.MUSIC KEEP
song_gdungn9 | Dungeons.MUSIC CHANGECut, replaced by song_d8 (not previously used)
song_geerie | Overworld, night. Seems to play in context of ruins.MUSIC KEEP
song_ggood | Temples.MUSIC CHANGECut, replaced by song_23
song_gmage_3 | Mage's Guild.AMBIENT MGCut
song_gneut | Temples.MUSIC CHANGECut, replaced by song_d7 (not previously used)
song_gpalac | Overworld foggy and castles.MUSIC CHANGEReplaces song_06, replaced by song_06
song_gruins | Overworld, night. Seems to play in context of ruins.AMBIENT NIGHTCut
song_gshop | Almost all shops.AMBIENT TEMPLECut
song_gsneak2 | Sneaking.AMBIENT DUNGEONCut (not currently used)
song_gsnow__b | Overworld, snowing.MUSIC CHANGEReplaces song_13, replaced by song_21
song_gsunny2 | Overworld, clear day and cloudy.AMBIENT DAYCut
song_magic_2 | Mage's Guild.AMBIENT MGCut
song_overcast | Overworld, foggy.MUSIC CHANGECut, replaced by song_dag_6 (not previously used)
song_overlong | Overworld, rain. Longer version of overcast.MUSIC CHANGEReplaces title theme, replaced by song_swimming
song_oversnow | Overworld, snowing.MUSIC CHANGECut, replaced by song_25 (not previously used)
song_raining | Overworld, rain.MUSIC KEEP
song_sneaking | Sneaking.AMBIENT DUNGEONCut (not currently used)
song_sneakng2| SneakingAMBIENT DUNGEONCut (not currently used)
song_snowing | Overworld, snowing.MUSIC CHANGECut, replaced by song_12
song_square_2 | Taverns.AMBIENT TAVERNCut
song_sunnyday | Overworld, clear day and cloudy.AMBIENT DAYCut (very similar to overcast/overlong)
song_swimming | Overworld, clear day and cloudy.AMBIENT DAYReplaces song_overlong
song_tavern | Taverns.MUSIC KEEP

Note: The sneaking songs are not presently used in game. In case they are implemented in the future, they are included (replaced by discrete ambient background noise) for completeness.