Upbeat tracks with brass-section:
The Sound - Words Fail Me - I mean, it's as upbeat as you can get with The Sound
The Honeymoon Killers - Fonce à Mort - More quirky and fast-paced than happy-go-lucky, but it has some brassy goodness in there.
Material Girls - Tightrope Same ilk as The Honeymoon Killers. Fast-paced and quirky. But seedy and erratic lyrics-wise. Kind of James Chance-esque with a slightly poppier sentiment.
KONK - Your Life - Life-affirming 80s Dance-number.
A Tribe Called Quest - Excursions - That beat is a pure manifestation of the warm and fuzzies.
Thelonious Monk - Misterioso - Some actual Jazz maybe? I find this one quite uplifting
And that's about all of the more upbeat brassy stuff I can come up with right now that isn't just straight-up Jazz (except for the bonus monk number).
As for generally upbeat/uplifting stuff:
Camper Van Beethoven - Life Is Grand - I know they aren't exactly popular on this board, but hey, they have a few awesome tunes. This one's unapologetically optimistic.
The Magnetic Fields - Long Forgotten Fairytale As with most Magnetic Fields songs, the lyrics aren't exactly feel-good. But I'll be damned, if this doesn't sound like a high-energy mashup between Erasure and OMD.
The Garden Club - Little Girl Lost And Found Obscure little psychedelic gem from the late 60s, apparently a micro-genre some call "Toytown". Vocals by Ruthann Friedman (writer of the massive 60s Association smash-hit "Windy)
Ruthann Friedman - Windy - And while we're at it - the writer performing her song, completely blowing the more well-known chart-topper version out of the water.
Cornelius - Perfect Rainbow - Shibuya Kei is probably one of the go-to genres for upbeat melodies. Also, not in the English language for once
The Pillows - Happy Bivouac More Japanese goodness.
Hi-Posi - You Are My Music Let's triple down on the Japanese goodness. This is super sugarcoated. I guess it's upbeat, but it's also quite weird in it's 90s candystore kind of way. Actually quite surreal in its reverance for kitsch. But damn is it catchy. And that outro is absolutely fucking gorgeous.
Velocity Girl - Audrey's Eyes Themes of loss notwithstanding - this one of those gorgeously bubbly and warm sounding 90s alternative songs.
Clouds - Sweetest Thing Somewhat some vein as Velocity Girl. Little known Aussie-band though.
Eve's Plum - Jesus Loves You (Not As Much As I Do) In keeping with bubbly 90s stuff - upping the ante on the bubblegum here. A bit of a guilty pleasure of mine. Yes, that's Vitamin C before she threw all pretension out of the window and went full Pop.
The Meters - Cissy Strut An absolute classic. Had to think of it when I saw symbols mention New Orleans music.
The Blue Hearts - Mirai Wa Bokura No Te No Naka - Additional Japanese goodness. Punk this time. The title translates to "The Future Is In Our Hands" - a stark contrast to the "No Future"-ethos that's been floating around in that genre.