Why has Katie started 'singing' at night?!

[Millys Mum]

Lola goes through stages of this and its always with a new 'toy of the month' she carries it around wailing and churping, i ignore her and eventually she will shut up. She does it whenever a new thing is caught, straws and carnations are a dead cert for her to start 
Personally i think its a come look what iv got for you noise 

[Purrlishious]

Mmm... Strange J.
My Poppy does that kind of singing thing during the night when she is downstairs & never during the day. It is different to the 'normal' noises. I put it down to her wanting me to get up, but if I did she would just run away... like she knows she wins! 
Cant offer a solution I'm afraid, is she playing with a toy at the time do you know?

[wharfevalley catsprotection]

When we started to try and keep Katie out of the bedroom at night, she used to cry and cry at our door and we soon learnt that it was easier to let her in 

That's fine as she tends to actually stay in the living room, but kind of likes to know that she can get to us if needs be. Now, she has started a new thing of 'singing' in the living room when she's playing at night! She used to do it sporadically when we first go her, but now it's quite annoying! We only live in a one bedroomed flat and so you can't really block out the sound! I just wondered if anyone knew why they do this?

It's a very different sound to a demanding miaow or a plaintive cry, it's more... melodic if that makes sense????!!!   

Is it just that she's enjoying herself or can it mean something else as well?

J xxx