It was apparently time for Britney Spears to clean house ... but not before she took a rare moment to actually sing for her fans on Instagram.

Brit posted a new video Monday morning ... and it was pretty shocking, since she usually just shares risqué, nearly-nude dances from inside her home -- never uttering a peep.

It's hard to say how much effort she was putting into singing -- it's arguably a tad shrill -- but she was having fun, adding the caption ... "Messing around with lighting and cleaning my house like no tomorrow 😳😳😳😂😂😂."

We would have thought she'd have staff for that ... worth noting, Britney is not alone while singing -- if you keep an eye on the background, a rabbit can be seen wandering around her place. Play video content

Last week, the singer-songwriter sh

See Full Page