July 14 (Reuters) - Social audio app Clubhouse launched a direct messaging feature on Wednesday called "Backchannel" to allow one-to-one and group text chats. The invite-only app, which saw explosive early growth during the COVID-19 pandemic, is now competing against a raft of tech companies from Facebook (FB.O) and Twitter (TWTR.N) to Spotify (SPOT.N) pushing out similar audio chat services. Clubhouse said it had added more than 8 million new users since launching on Android in late May. It said the ability to direct message was one of its most requested features.