diff --git a/pkgs/by-name/jc/jc303/package.nix b/pkgs/by-name/jc/jc303/package.nix
new file mode 100644
index 000000000000..df589c158785
--- /dev/null
+++ b/pkgs/by-name/jc/jc303/package.nix
@@ -0,0 +1,186 @@
+{
+  stdenv,
+  fetchFromGitHub,
+  fetchpatch,
+  lib,
+  cmake,
+  pkg-config,
+  writableTmpDirAsHomeHook,
+  nix-update-script,
+  juce,
+  libx11,
+  libxrandr,
+  libxinerama,
+  libxext,
+  libxcursor,
+  freetype,
+  fontconfig,
+  alsa-lib,
+
+  buildVST3 ? true,
+  buildLV2 ? true,
+  buildCLAP ? true,
+}:
+
+let
+  juce-clap-extensions = fetchFromGitHub {
+    owner = "free-audio";
+    repo = "clap-juce-extensions";
+    rev = "02f91b7988298f7f1f05c706da16e1d9da852a87";
+    hash = "sha256-cPi+prl+jLq/KvjZ5M2MxxZVLSKCiJB9SQHK8psW2OU=";
+    fetchSubmodules = true;
+  };
+
+  chowdsp_utils = fetchFromGitHub {
+    owner = "Chowdhury-DSP";
+    repo = "chowdsp_utils";
+    rev = "ffc70ba399f9afaeefb996eb14e55a1d487270b8"; # LIB_CHOWDSP_UTILS_TAG from CMakeLists.txt
+    hash = "sha256-rKjrhb+w/lW9k3Dg5jWM2eJRa0fPDF8SNVrCTFrRMoM=";
+  };
+
+  # src/dsp/guitarml-byod/CMakeLists.txt
+  rtneural = fetchFromGitHub {
+    owner = "jatinchowdhury18";
+    repo = "RTNeural";
+    rev = "04cb333bc4b174760958a77c7ce076eae38fe8e4"; # LIB_RTNEURAL_TAG
+    hash = "sha256-kTHYEpoXPYNKEs7rHeSwBHVQnOQKhKnST+UWa++uCsc=";
+    fetchSubmodules = true;
+
+    postFetch = ''
+      # note: if rtneural is updated, this won't be needed anymore
+      substituteInPlace $out/CMakeLists.txt \
+        --replace-fail "include(cmake/CPM.cmake)" "# No tests" \
+
+      # Required for CMake 4
+      substituteInPlace $out/CMakeLists.txt \
+        --replace-fail \
+          "cmake_minimum_required(VERSION 3.5)" \
+          "cmake_minimum_required(VERSION 4.0)"
+    '';
+  };
+
+  # src/dsp/guitarml-byod/CMakeLists.txt
+  math_approx = fetchFromGitHub {
+    owner = "Chowdhury-DSP";
+    repo = "math_approx";
+    rev = "0c68d4d17242d707ba07fa7f1901692b7ed72d58"; # LIB_CHOWDSP_MATH_APPROX_TAG
+    hash = "sha256-t6UrsZGRJjJVp+aGkwBa++Skj9xkdQuZKAxRrTkfM0E=";
+  };
+
+  # src/dsp/guitarml-byod/CMakeLists.txt
+  ea_variant = fetchFromGitHub {
+    owner = "eyalamirmusic";
+    repo = "Variant";
+    rev = "3fce49cfca50ba3b05026d41ffc4911a8e653378"; # LIB_VARIANT_TAG
+    hash = "sha256-2zzam7rKY6zoT2jFqDtr4pwOCAWTu0GTxUqVGxVHbQQ=";
+  };
+
+  formats = lib.concatStringsSep " " [
+    (lib.optionalString buildVST3 "VST3")
+    (lib.optionalString buildLV2 "LV2")
+  ];
+in
+stdenv.mkDerivation (finalAttrs: {
+  pname = "jc303";
+  version = "0.12.3";
+
+  src = fetchFromGitHub {
+    owner = "midilab";
+    repo = "jc303";
+    tag = "v${finalAttrs.version}";
+    hash = "sha256-5OA7ir8loT0Lx05guwuZNCW9J9I3TA5+A9JZ9E7oWXA=";
+  };
+
+  patches = [
+    # `BUILD_CLAP` cmake flag
+    (fetchpatch {
+      url = "https://github.com/midilab/jc303/commit/837d3fc5cf4e993375403a45d7e23df1b4e3cf7f.diff";
+      hash = "sha256-WvLIcSHrLiXj1VEV+IxS05YSWEq7oz57qIbNsqRySaY=";
+    })
+  ];
+
+  postPatch = ''
+    substituteInPlace CMakeLists.txt \
+      --replace-fail "set(PLUGIN_FORMATS AU VST3 LV2)" "set(PLUGIN_FORMATS ${formats})" \
+  '';
+
+  nativeBuildInputs = [
+    cmake
+    pkg-config
+    writableTmpDirAsHomeHook
+  ];
+
+  buildInputs = [
+    libx11
+    libxrandr
+    libxext
+    libxcursor
+    libxinerama
+    freetype
+    fontconfig
+    alsa-lib
+  ];
+
+  cmakeFlags = [
+    # CMakeLists.txt
+    (lib.cmakeFeature "FETCHCONTENT_SOURCE_DIR_JUCE" "${juce.src}")
+    (lib.cmakeFeature "FETCHCONTENT_SOURCE_DIR_JUCE-CLAP-EXTENSIONS" "${juce-clap-extensions}")
+    (lib.cmakeFeature "FETCHCONTENT_SOURCE_DIR_CHOWDSP_UTILS" "${chowdsp_utils}")
+
+    # src/dsp/guitarml-byod/CMakeLists.txt
+    (lib.cmakeFeature "FETCHCONTENT_SOURCE_DIR_RTNEURAL" "${rtneural}")
+    (lib.cmakeFeature "FETCHCONTENT_SOURCE_DIR_MATH_APPROX" "${math_approx}")
+    (lib.cmakeFeature "FETCHCONTENT_SOURCE_DIR_EA_VARIANT" "${ea_variant}")
+
+    (lib.cmakeBool "BUILD_CLAP" buildCLAP)
+  ];
+
+  # Fontconfig error: Cannot load default config file: No such file: (null)
+  env.FONTCONFIG_FILE = "${fontconfig.out}/etc/fonts/fonts.conf";
+
+  enableParallelBuilding = true;
+
+  env.NIX_CFLAGS_COMPILE = lib.optionalString stdenv.hostPlatform.isLinux (toString [
+    # juce, compiled in this build as part of a Git submodule, uses `-flto` as
+    # a Link Time Optimization flag, and instructs the plugin compiled here to
+    # use this flag to. This breaks the build for us. Using _fat_ LTO allows
+    # successful linking while still providing LTO benefits. If our build of
+    # `juce` was used as a dependency, we could have patched that `-flto` line
+    # in our juce's source, but that is not possible because it is used as a
+    # Git Submodule.
+    "-ffat-lto-objects"
+  ]);
+
+  installPhase = ''
+    runHook preInstall
+
+    pushd JC303_artefacts/Release
+      ${lib.optionalString buildVST3 ''
+        mkdir -p $out/lib/vst3
+        cp -r VST3/JC303.vst3 $out/lib/vst3
+      ''}
+
+      ${lib.optionalString buildCLAP ''
+        mkdir -p $out/lib/clap
+        cp -r CLAP/JC303.clap $out/lib/clap
+      ''}
+
+      ${lib.optionalString buildLV2 ''
+        mkdir -p $out/lib/lv2
+        cp -r LV2/JC303.lv2 $out/lib/lv2
+      ''}
+    popd
+
+    runHook postInstall
+  '';
+
+  passthru.updateScript = nix-update-script { };
+
+  meta = {
+    description = "Roland TB-303 clone plugin";
+    homepage = "https://github.com/midilab/jc303";
+    platforms = lib.platforms.linux;
+    license = lib.licenses.gpl3Plus;
+    maintainers = [ lib.maintainers.mrtnvgr ];
+  };
+})