Guitar Hero Live

Go into Guitar Hero TV which is the option "TV" option on the right (Not "LIVE" which is on the left). Now you can get this either playing songs in the channels or playing the songs on demand using "plays" but what can be confusing is that the 24 hours is only counted when playing a song. Even though you are logged into TV mode you can't just walk away and leave your guitar on, you have to actually be playing a song. This also goes for the channels, when you are between songs and it has the mini commercials, that doesn't count towards the 24 hours. Neither does going through the song catalog in the on demand section.

To sum it all up you need 24 hours in GHTV playing songs. Everything else doesn't count.

A side note, when you check the leaderboards in either the Game Hub or Compared to Friends option, that count is your total amount of time in GHTV not just the time spent playing songs so this can be misleading. You can track the achievement in the in game achievement option. Press "3" from the opening menu where you can choose from either "LIVE" or "TV" and go down the the achievement option. It will show you how many seconds you have out of 86400 which is how many seconds are in 24 hours.

If you really don't want to play the songs, you can tape down one of the buttons on the guitar and occasionally strum so the guitar doesn't turn off. This isn't a perfect solution for this as the game will eventually kick you out, but it's the easiest way without playing the songs as far as I can tell.

My advice would be, however, not to bother and just play as normal if you're going for the 100,000,000, Level 20 and 1,000 Hero Power achievements too, as those three popped about an hour before this for me.