message: exporting FrequencyEnvelope
diff: @@ -18,6 +18,7 @@ export * from "./channel/Split";
  export * from "./dynamics/Compressor";
  export * from "./envelope/AmplitudeEnvelope";
  export * from "./envelope/Envelope";
  +export * from "./envelope/FrequencyEnvelope";
  export * from "./envelope/ScaledEnvelope";
  export * from "./filter/EQ3";
  export * from "./filter/Filter";
  