One voice to rule them all? That's not Microsoft's or Amazon's plan, as the two have been working for almost nine months to let Cortana users access Alexa and Alexa users access Cortana.

Microsoft is showing off the ability, even though it is in beta tests for now. For Cortana users, this means accessing Alexa to make purchases, for example, on Amazon. It will also allow Alexa users to send emails through their Microsoft account.

Cortana is the smart voice assistant developed by Microsoft and found on Outlook, built into Windows 10, and also found in the Harman Kardon Invoke smart speaker launched in 2017. Alexa is Amazon's voice assistant and the dominant A.I. now used in smart home devices, including smart speakers like Amazon's Echo, and its Echo Show, along with a host of other products from smart lights like C by GE Sol to the ecobee4 smart thermostat.

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The digital assistant race is a real. Amazon Alexa and Google Assistant are the dominant voice systems, for now. Apple's Siri, Microsoft's Cortana and Samsung's Bixby are further back in the pack. Microsoft aligning itself with Amazon may give its digital assistant a bit of an edge — and there's a good reason they're all vying for the top spot: nearly half of all people in the U.S. use a voice assistant, according to the Pew Research Center.

Microsoft gave a little demo of the new friendship at its annual event Microsoft Build in Seattle, WA, which started May 7. Tom Taylor, senior vice president of Amazon Alexa took the stage along with Megan Saunders, general manager of Cortana and had the two A.I.'s carry on a little love fest, asking "Alexa, what do you think about Cortana?" To which Cortana replied: "I like Cortana. We both have experience with light rings, although hers is more of a halo."

People will be able to open Alexa inside a Cortana device by saying, "Cortana, open Alexa." A similar phrase will work to get Cortana on an Alexa-enabled product.

Anyone interested in learning more about the Cortana and Alexa mashup can sign up on Microsoft's site to receive information as the company makes the feature available.

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