public Builder clearMultiSpeakerMarkup() {
      if (multiSpeakerMarkupBuilder_ == null) {
        if (inputSourceCase_ == 4) {
          inputSourceCase_ = 0;
          inputSource_ = null;
          onChanged();
        }
      } else {
        if (inputSourceCase_ == 4) {
          inputSourceCase_ = 0;
          inputSource_ = null;
        }
        multiSpeakerMarkupBuilder_.clear();
      }
      return this;
    }
<pre>
The multi-speaker input to be synthesized. Only applicable for
multi-speaker synthesis.
</pre>

<code>.google.cloud.texttospeech.v1beta1.MultiSpeakerMarkup multi_speaker_markup = 4;</code>
java-texttospeech/proto-google-cloud-texttospeech-v1beta1/src/main/java/com/google/cloud/texttospeech/v1beta1/SynthesisInput.java