Elon Musk, the billionaire founder of electric vehicle maker Tesla, plans to sell a song he posted online as a non-fungible token (NFT) as the blockchain-authenticated digital tokens gain traction. Mr Musk, who recently declared himself the technoking of Tesla, shared the 140-second song in a tweet that has been viewed by over 6.1 million people. “I’m selling this song about NFTs as an NFT,” the billionaire tweeted. “I love music. It makes my heart sing.” Mr Musk’s song is a techno track that refers repeatedly to the digital-only assets, saying “NFT for your vanity, computers never sleep, it's verified, it's guaranteed”. The song features a rotating golden trophy with the text ‘vanity trophy’ circling around it. It also displays ‘HODL’ (hold on for dear life) at the bottom that is commonly used by traders who invest in digital assets. An NFT is a unique digital token that can turn any item in the digital world from tweets to gifs and from artworks to videos into a tangible asset. Like Bitcoin and other cryptocurrencies, they are sold and brought through the blockchain. They are not interchangeable and their authenticity is verified by encrypting the creator's signature on the blockchain. They are usually created by uploading files to online auction platforms like Valuables. "Owning any digital content can be a financial investment, hold sentimental value and create a relationship between collector and creator," said <a href="https://v.cent.co/">Valuables</a>. "The tweet itself will continue to live on Twitter ... what you are purchasing is a digital certificate of the tweet, unique because it has been signed and verified by the creator.” Mr Musk did not include a link to the NFT in his tweet, so it is not clear when he is aiming to sell and on which platform. Tesla's stock closed 2.05 per cent up at $707.94 per share on Monday. Tesla aims to invest a portion of its cash in alternative assets including digital assets, gold bullion and gold exchange-traded funds as it diversifies its holdings. Last month, it said in a <a href="https://www.thenationalnews.com/business/technology/tesla-invests-1-5bn-in-bitcoin-and-will-accept-cryptocurrency-as-payment-1.1162252">filing</a> that it will soon accept Bitcoin as payment for its electric vehicles and has invested $1.5 billion in the biggest cryptocurrency.