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While all of these options are always available, the options are condensed to those unique actions and presented to the connected client in a number of ways. In other words, when the queue is empty, the only presented option is Now because there is nothing to modify. Sending Replace in such a scenario would perform the same exact action as Now. The list of options is communicated to the connected client via the LocalQueueOptions status event or as a menu when indicating playback via the ClarifyTitleIntent command. To ensure MMS knows the client supports this functionality, be sure to indicate as such by sending SetOption supports_playnow=true during the preamble. See the Setting Additional Options section above for more details.
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