I can empathise with that.   I don't play cello much at all, mostly fiddle. 

With the fiddle, even indoors, I detest sitting down to play, and I will invariably stand - it gives that extra freedom to move somewhat (because, well, I like to !) and to really "work" with the bow and interact better with the instrument ( I know, it can be frowned upon by violinists, but I'm a fiddler!) .  And as for outdoors  - I love that.   Indoors, I will play either in my music room, which, by intent is quite an echo-y room (hard flooring, no soft furnishings - so lots of local echo/reverb - which - to a point, I like).  There are times, that is "too much" and I'll specifically choose to play in the lounge - it's carpeted, has soft furnishings and heavy drape curtains.  That "calms the tone down" substantially.

But, playing outdoors is just awesome - even in the soft-furnished lounge, sure there are hard surface walls and ceilings, creating some degree of reflected sound feedback to the ear.  Outdoors - that disappears totally - and - particularly with the fiddle which has a lot of high-end harmonics in the generated sound - the "sharpness" goes completely - it's like a different instrument.  It also allows me to wander-around while playing which I also like to do. ( OK, might be a problem for a cello - maybe fit little wheels !! ).    When I hosted "The Traveler" I recorded most of my videos outside - in a car park with wonderful scenery behind, on a beach, on a pier, atop a small hill and so on - and sure - although MY concentration was clearly focussed on playing, there was just this additional simple sense of pleasure in being there, that hopefully came through in my playing !

LOL - @ELCBK - 

... then I had a horrible vision of a brass quartet standing out in a Winter storm, trying to play "O Holy Night" - lips frozen to mouth pieces & fingers like icicles stuck to valves and tubing. 

You paint a fine picture of how musicians are so totally dedicated to their art.

And @Gordon Shumway 

Or maybe I'd microwave two potatoes before going out and put each in a sock with a mouthpiece in my coat pockets.

 Yeah, and a snack for lunch !  Serves a dual purpose, and no waste.   Cool !!!!

Wow, @Gordon Shumway - indeed - Cider with Rosie, that just rings a bell - oh - like close on 50 years after originally having read it ( I revisited it, oh, probably 15, 17 years back or so n film...  the one with Patrick ( or do I mean David? ) Troughton.... yup - that's the reference !!!! Man, well done !!!!  Jings, memory triggers, or what ?   Still going "wowww"   Neat.