Spotify is putting song lyrics behind a paywall, prompting users to switch to Spotify Premium for full access.The move is likely an attempt to push more users towards the Premium tier and potentially prepare for the launch of a rumored Supremium tier.Screenshots of Spotify Supremium leaked, indicating an 'Enhanced Listening' tier offering lossless audio on compatible devices.Spotify is also expected to increase subscription charges in the US, following previous price hikes in other markets.