diff --git a/supriya/ext/mypy.py b/supriya/ext/mypy.py
index 599c60d0d..2d6fb1f8c 100644
--- a/supriya/ext/mypy.py
+++ b/supriya/ext/mypy.py
@@ -48,9 +48,7 @@ def transform(self) -> bool:
         print("B", output_proxy, type(output_proxy))
 
         # Union[Default, OutputProxy, SupportsFloat]
-        init_scalar_param_type = make_simplified_union(
-            [supports_float, output_proxy]
-        )
+        init_scalar_param_type = make_simplified_union([supports_float, output_proxy])
         print(init_scalar_param_type)
         # Sequence[Union[OutputProxy, SupportsFloat]]
         init_vector_param_type = make_simplified_union(
diff --git a/supriya/synthdefs/envelopes.py b/supriya/synthdefs/envelopes.py
index 257ebaa6c..0552d145b 100644
--- a/supriya/synthdefs/envelopes.py
+++ b/supriya/synthdefs/envelopes.py
@@ -27,8 +27,8 @@ def __init__(
         amplitudes: Sequence[Union[SupportsFloat, OutputProxy]] = (0, 1, 0),
         durations: Sequence[Union[SupportsFloat, OutputProxy]] = (1, 1),
         curves: Sequence[Union[EnvelopeShapeLike, OutputProxy, SupportsFloat]] = (
-            "linear",
-            "linear",
+            EnvelopeShape.LINEAR,
+            EnvelopeShape.LINEAR,
         ),
         release_node: Optional[int] = None,
         loop_node: Optional[int] = None,
@@ -221,7 +221,7 @@ def serialize(self, for_interpolation=False) -> UGenArray:
                     shape = 5
                 result.append(shape)
                 result.append(curve)
-        return UGenArray(result)
+        return result
 
     @classmethod
     def triangle(cls, duration=1.0, amplitude=1.0) -> "Envelope":
diff --git a/supriya/ugens/bases.py b/supriya/ugens/bases.py
index efcbdb549..8fdac8a73 100644
--- a/supriya/ugens/bases.py
+++ b/supriya/ugens/bases.py
@@ -44,7 +44,7 @@ class Param(NamedTuple):
 
 
 class UGenSerializable(Protocol):
-    def serialize(self) -> "UGenOperable":
+    def serialize(self) -> Sequence[Union[SupportsFloat, "OutputProxy"]]:
         pass