Apple has opened exploratory talks with senior label executives about the possibility of launching an on-demand streaming service that would rival Spotify and Beats Music, according to three people familiar with the talks. Apple is also thinking about adding an iTunes App for Android phones, the Google rival that has been growing faster than the iPhone, these sources said. The surprising discussions are part of a multi-pronged strategy to deal with the double-digit decline in U.S. download sales at Apple’s iTunes Music Store, the largest music retailer.