We love ambience, but it lacks a lot of features that we really wanted in 1.12.2. This was only built for a pack in 1.12.2, however it's fairly easy to update if anyone needs it. Here is a list of the features.

Smooth Transitions between songs
Music continues to play even if the game is totally busy. (Will still pause during stw GCs)
Fully fleshed out tagging system to help play your songs only when the time is right
Smart queue that handles priority, sudden tracks (such as combat music), and logic such as !storm&outside
Resumes where it left off (say you go underground, then back to the surface. Surface music will resume where it left off so using 2 hour long tracks is fine because it wont keep restarting!)
Play music during forge setup!
JSON Conditions hotload so you can hear your changes when the file is saved.

Resonance is a CLIENTSIDE ONLY MOD. Do not place this on servers, as it may crash on startup!

List of Tags

A list of updated tags can be found in .minecraft/resonance/help.txt. Adding mods that include biomes will also add to this list, so check your own tags instead of relying on this one.

Depending on what the player is doing ingame, different triggers will activate and deactivate.
Multiple triggers can be active at once. When triggers change, the queue of music changes.
Below is a list of triggers that happen and their description.

=== TAG CONDITIONS ===
The json config contains all tags by default as separate conditions. If you assume the tag name is 'biome_plains'
biome_plains = Condition met if the tag is active
!biome_plains = Condition is met if tag is INACTIVE
biome_* = If any tag active starts with biome_ (such as bione_plains) or (biome_desert)
!biome_mesa* = If any tag inactive starts with biome_mesa (such as bione_mesa) or (biome_mesa_rock)

=== TAGS ===
light_bright - High light...
biome_taiga_cold_hills - When in the Cold Taiga Hills Biome
biome_swampland - When in the Swampland Biome
height_bedrock - Below 35
biome_river - When in the River Biome
lush_normal - Medium amounts of foliage, & greens
lush_barren - Little to no foliage / greens
biome_mutated_mesa_clear_rock - When in the Mesa Plateau M Biome
time_day - Day time...
biome_extreme_hills - When in the Extreme Hills Biome
biome_sky - When in the The End Biome
humid_dry - Dry biome
temp_freezing - Frozen biome
biome_mushroom_island_shore - When in the MushroomIslandShore Biome
biome_mutated_swampland - When in the Swampland M Biome
biome_plains - When in the Plains Biome
biome_mesa_clear_rock - When in the Mesa Plateau Biome
temp_chilly - Cold biome
biome_mutated_plains - When in the Sunflower Plains Biome
startup.init - Forge is starting up (mid)
biome_cold_beach - When in the Cold Beach Biome
fp_low - Food below 30%
biome_taiga_hills - When in the TaigaHills Biome
dead - Death screen
biome_ice_flats - When in the Ice Plains Biome
biome_roofed_forest - When in the Roofed Forest Biome
biome_savanna - When in the Savanna Biome
time_night - Night time...
biome_mutated_birch_forest - When in the Birch Forest M Biome
biome_frozen_river - When in the FrozenRiver Biome
biome_frozen_ocean - When in the FrozenOcean Biome
hp_low - HP Below 30%
world - Anytime you are ingame (in any world)
biome_mutated_redwood_taiga - When in the Mega Spruce Taiga Biome
temp_hot - Hot biome
biome_mutated_mesa_rock - When in the Mesa Plateau F M Biome
biome_birch_forest - When in the Birch Forest Biome
biome_mutated_jungle_edge - When in the JungleEdge M Biome
temp_warm - Warm biome
temp_superhot - Very hot biome
storm - If it's raining in the world & the current biome supports rain
biome_smaller_extreme_hills - When in the Extreme Hills Edge Biome
biome_desert_hills - When in the DesertHills Biome
menu - Game is in the main menu
height_sohigh - At or above 200
light_dark - Darkness
biome_redwood_taiga_hills - When in the Mega Taiga Hills Biome
biome_void - When in the The Void Biome
biome_mutated_mesa - When in the Mesa (Bryce) Biome
light_mid - Middle range light
biome_mesa_rock - When in the Mesa Plateau F Biome
biome_mushroom_island - When in the MushroomIsland Biome
lush_dense - Lots of foliage, & greens
dim1 - When in the_end Dimension.
biome_mutated_savanna - When in the Savanna M Biome
dim0 - When in overworld Dimension.
biome_birch_forest_hills - When in the Birch Forest Hills Biome
thunder - If it's thundering in a biome where rain / snow can happen
biome_deep_ocean - When in the Deep Ocean Biome
biome_ice_mountains - When in the Ice Mountains Biome
startup - Forge is starting up
biome_forest_hills - When in the ForestHills Biome
dim-1 - When in the_nether Dimension.
biome_mutated_extreme_hills_with_trees - When in the Extreme Hills+ M Biome
biome_extreme_hills_with_trees - When in the Extreme Hills+ Biome
biome_jungle - When in the Jungle Biome
biome_taiga - When in the Taiga Biome
startup.preinit - Forge is starting up (pre)
biome_mutated_jungle - When in the Jungle M Biome
biome_mutated_ice_flats - When in the Ice Plains Spikes Biome
biome_beaches - When in the Beach Biome
height_sealevel - Below 94
biome_mesa - When in the Mesa Biome
biome_mutated_taiga_cold - When in the Cold Taiga M Biome
humid_mild - Normal Humidity
height_high - Below 200
biome_savanna_rock - When in the Savanna Plateau Biome
biome_mutated_birch_forest_hills - When in the Birch Forest Hills M Biome
biome_mutated_roofed_forest - When in the Roofed Forest M Biome
biome_jungle_edge - When in the JungleEdge Biome
biome_redwood_taiga - When in the Mega Taiga Biome
biome_jungle_hills - When in the JungleHills Biome
humid_wet - Wet biome
biome_mutated_redwood_taiga_hills - When in the Redwood Taiga Hills M Biome
biome_hell - When in the Hell Biome
biome_mutated_taiga - When in the Taiga M Biome
biome_mutated_savanna_rock - When in the Savanna Plateau M Biome
biome_mutated_extreme_hills - When in the Extreme Hills M Biome
biome_mutated_desert - When in the Desert M Biome
height_low - Below 60
biome_ocean - When in the Ocean Biome
biome_stone_beach - When in the Stone Beach Biome
biome_forest - When in the Forest Biome
biome_taiga_cold - When in the Cold Taiga Biome
startup.postinit - Forge is starting up (post)
biome_desert - When in the Desert Biome
biome_mutated_forest - When in the Flower Forest Biome

You can use the above tags (spoiler) to define groups of music to be played during that time. Take a look at the example (spoiler) below.

{
 "conditions": [
 {
 "when": [
 "menu"
 ],
 "play": [
 "FinalStand.mp3"
 ]
 },
 {
 "when": [
 "world",
 "!hp_low",
 "!fp_low",
 "dim0",
 "time_night",
 "!storm",
 "height_sealevel"
 ],
 "mode": "AND",
 "play": [
 "Skyrim/SkyrimAtmospheres.mp3",
 "Skyrim/AWintersTale.mp3",
 "Skyrim/DeathintheDarkness.mp3",
 "Skyrim/FromPasttoPresent.mp3",
 "Skyrim/Frostfall.mp3",
 "Skyrim/SilentFootsteps.mp3",
 "Skyrim/Secunda.mp3",
 "Skyrim/SkyAboveVoiceWithin.mp3",
 "Skyrim/Tundra.mp3",
 "Skyrim/Unbound.mp3",
 "DOS2/QuirkyBones.mp3",
 "DOS2/Reflections.mp3"
 ]
 }
 ]
}

Songs are placed in the music folder (.minecraft/resonance/music). You can use subfolders so long as you include the .mp3 extension. Only MP3s are supported currently to remain cross platform.

Note: We use JavaFX as our player by shoving a JavaFX jar into the classpath at runtime. This should be compatible with all versions of java but let us know if there are any issues.

Source (GitHub)