diff --git a/src/tinysoundfont/__init__.py b/src/tinysoundfont/__init__.py
index 6050a8b..aaaf8c6 100644
--- a/src/tinysoundfont/__init__.py
+++ b/src/tinysoundfont/__init__.py
@@ -1,2 +1,7 @@
-from .synth import Synth, SoundFontException
-from .sequencer import Sequencer
+from .synth import (
+    Synth as Synth,
+    SoundFontException as SoundFontException,
+)
+from .sequencer import (
+    Sequencer as Sequencer,
+)
diff --git a/src/tinysoundfont/__main__.py b/src/tinysoundfont/__main__.py
index 6abd420..b96c16b 100644
--- a/src/tinysoundfont/__main__.py
+++ b/src/tinysoundfont/__main__.py
@@ -2,7 +2,7 @@
 import sys
 import time
 
-from .synth import Synth, SoundFontException
+from .synth import Synth
 from .sequencer import Sequencer
 
 
diff --git a/src/tinysoundfont/midi/__init__.py b/src/tinysoundfont/midi/__init__.py
index 51b9791..a0cfc6c 100644
--- a/src/tinysoundfont/midi/__init__.py
+++ b/src/tinysoundfont/midi/__init__.py
@@ -175,7 +175,7 @@ def load_memory(
         event.t += delta_time
         event.persistent = persistent
         if filter is not None:
-            if filter(event) == True:
+            if filter(event):
                 event = None
         # Check for None return value in filtered events, don't add if None
         if event is not None:
diff --git a/src/tinysoundfont/sequencer.py b/src/tinysoundfont/sequencer.py
index 4eac875..29d8b00 100644
--- a/src/tinysoundfont/sequencer.py
+++ b/src/tinysoundfont/sequencer.py
@@ -8,12 +8,11 @@
 #
 
 from collections import deque
-from typing import Callable, List, Optional
+from typing import List
 from .synth import Synth
 from .midi import (
     load,
     Event,
-    Action,
     NoteOn,
     NoteOff,
     ControlChange,
diff --git a/test/example_midi_filter.py b/test/example_midi_filter.py
index 4ad9089..de9ccb4 100644
--- a/test/example_midi_filter.py
+++ b/test/example_midi_filter.py
@@ -8,7 +8,7 @@
 def filter_program_change(event):
     """Make all program changes go to preset 19"""
     match event.action:
-        case tinysoundfont.midi.ProgramChange(program):
+        case tinysoundfont.midi.ProgramChange(_program):
             event.action.program = 19 # Church organ
 
 seq = tinysoundfont.Sequencer(synth)
diff --git a/test/test_synth.py b/test/test_synth.py
index 3c2b1db..abe342e 100644
--- a/test/test_synth.py
+++ b/test/test_synth.py
@@ -75,7 +75,7 @@ def test_0():
     def filter_program_change(event):
         """Make all program changes go to preset 40 (violin)"""
         match event.action:
-            case tinysoundfont.midi.ProgramChange(program):
+            case tinysoundfont.midi.ProgramChange(_program):
                 event.program = 40
     seq = tinysoundfont.Sequencer(synth)
     seq.midi_load("test/1080-c01.mid", filter=filter_program_change)
@@ -90,7 +90,7 @@ def test_midi_generate():
     import numpy as np
 
     synth = tinysoundfont.Synth()
-    sfid = synth.sfload("test/florestan-subset.sfo")
+    _sfid = synth.sfload("test/florestan-subset.sfo")
 
     seq = tinysoundfont.Sequencer(synth)
     seq.midi_load("test/1080-c01.mid")