diff --git a/Util/Audio/OfflineAudioMixer.cs b/Util/Audio/OfflineAudioMixer.cs
index 0fa528b..17ee323 100644
--- a/Util/Audio/OfflineAudioMixer.cs
+++ b/Util/Audio/OfflineAudioMixer.cs
@@ -32,7 +32,10 @@ internal sealed class OfflineAudioMixer : IDisposable
     /// <summary>Additional gain of effect sounds (registered with <see cref="RegisterSoundEvent"/>).</summary>
     private const double EffectVolume = 2.0 / 3.0;
 
-    /// <summary>Number of tracked effect voices at which finished ones are removed from the list used by <see cref="StopAllEffects"/>.</summary>
+    /// <summary>
+    /// Smallest number of tracked effect voices at which finished ones are removed from the list used by <see cref="StopAllEffects"/>.
+    /// After each removal the next threshold is twice the remaining count (at least this value).
+    /// </summary>
     private const int EffectVoicePruneCount = 1024;
 
     /// <summary>Longest wait for a commit before checking for cancellation again, in milliseconds.</summary>
@@ -49,6 +52,7 @@ internal sealed class OfflineAudioMixer : IDisposable
     // Main thread.
     private ConditionalWeakTable<AudioSource, Voice> _sourceVoices = new();
     private readonly List<Voice> _effectVoices = new();
+    private int _effectVoicePruneAt = EffectVoicePruneCount;
     private AudioClipSource? _bgmSource;
     private string _bgmKey = "";
     private Voice? _bgmVoice;
@@ -193,8 +197,11 @@ internal sealed class OfflineAudioMixer : IDisposable
         var voice = _mixer.Play(clipSource, clipName, startTime, volume * ClipVolume * EffectVolume, pitch, loop, now);
         if (loop) voice.SetEndTime(endTime, now);
 
-        if (_effectVoices.Count >= EffectVoicePruneCount)
+        if (_effectVoices.Count >= _effectVoicePruneAt)
+        {
             _effectVoices.RemoveAll(v => v.IsFinished);
+            _effectVoicePruneAt = Math.Max(EffectVoicePruneCount, _effectVoices.Count * 2);
+        }
         _effectVoices.Add(voice);
 
         if (source) MapSource(source!, voice);