If it's a 'Freestyle' - ie no drums, guitars etc - then it effectively has no time signature or tempo.
I'm giving lesson in a few hours to someone who's using one of my Freestyles in an orchestral arrangement. Part of it is in 3/4, part in 6/8 and part in 2/4. The Freestyle covers them all perfectly. Although it has no tempo as such, he has lowered the indicated tempo down to a low value, so that the Harpeggio multi pad he's using runs nice and slow as well.