Initial release

Nexus page: https://www.nexusmods.com/stardewvalley/mods/13099

Caveats:
    - The music will go silent after dark (6-8pm depending on season).
    - There may be a short pause between each loop.
    - Music will not loop unless you are outdoors or in the mines.

SoundLoopMod/ModEntry.cs

@@ -0,0 +1,57 @@
+// SoundLoop Stardew Valley Mod
+// Copyright (C) 2022 strelkasaur
+//
+//     This program is free software: you can redistribute it and/or modify
+//     it under the terms of the GNU General Public License as published by
+//     the Free Software Foundation, either version 3 of the License, or
+//     (at your option) any later version.
+//
+//     This program is distributed in the hope that it will be useful,
+//     but WITHOUT ANY WARRANTY; without even the implied warranty of
+//     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+//     GNU General Public License for more details.
+//
+//     You should have received a copy of the GNU General Public License
+//     along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+using System;
+using Microsoft.Xna.Framework;
+using StardewModdingAPI;
+using StardewModdingAPI.Events;
+using StardewModdingAPI.Utilities;
+using StardewValley;
+using StardewValley.Locations;
+
+
+namespace SoundLoopMod
+{
+    public class ModEntry : Mod
+    {
+        public override void Entry(IModHelper helper)
+        {
+            helper.Events.GameLoop.OneSecondUpdateTicking += this.CheckMusicNeedsRestarting;
+        }
+
+        private void CheckMusicNeedsRestarting(object? sender, OneSecondUpdateTickingEventArgs e)
+        {
+            if (!Context.IsWorldReady)
+                return;
+            
+            MineShaft.timeSinceLastMusic = 999999;
+            
+            // Avoid playing morning song in the mines etc.
+            if (!Game1.currentLocation.IsOutdoors)
+                return;
+        
+            // The game keeps trying to stop the music if it's dark. We won't fight it for now
+            if (Game1.isDarkOut())
+                return;
+        
+            if (Game1.currentSong == null || Game1.currentSong.IsStopped || Game1.requestedMusicTrack.ToLower().Contains("ambient"))
+            {
+                Game1.playMorningSong();
+                this.Monitor.Log("Restarted music");
+            }
+        }
+    }
+}

SoundLoopMod/SoundLoopMod.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+    <PropertyGroup>
+        <TargetFramework>net5.0</TargetFramework>
+        <ImplicitUsings>enable</ImplicitUsings>
+        <Nullable>enable</Nullable>
+        <LangVersion>10</LangVersion>
+    </PropertyGroup>
+
+    <ItemGroup>
+      <PackageReference Include="Pathoschild.Stardew.ModBuildConfig" Version="4.0.1" />
+    </ItemGroup>
+
+</Project>

SoundLoopMod/manifest.json

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+{
+  "Name": "SoundLoop Mod",
+  "Author": "strelkasaur",
+  "Version": "1.0.0",
+  "Description": "Loops the in-game music",
+  "UniqueID": "com.strelkasaurus.sm.soundloop",
+  "EntryDll": "SoundLoopMod.dll",
+  "MinimumApiVersion": "3.0.0",
+  "UpdateKeys": ["Nexus:13099"]
+}