default io.grpc.stub.StreamObserver<
            com.google.cloud.texttospeech.v1beta1.StreamingSynthesizeRequest>
        streamingSynthesize(
            io.grpc.stub.StreamObserver<
                    com.google.cloud.texttospeech.v1beta1.StreamingSynthesizeResponse>
                responseObserver) {
      return io.grpc.stub.ServerCalls.asyncUnimplementedStreamingCall(
          getStreamingSynthesizeMethod(), responseObserver);
    }
<pre>
Performs bidirectional streaming speech synthesis: receive audio while
sending text.
</pre>
java-texttospeech/grpc-google-cloud-texttospeech-v1beta1/src/main/java/com/google/cloud/texttospeech/v1beta1/TextToSpeechGrpc.java