We can't help being sad from time to time, but it's not something I actively work on, with or without musical stimuli. Let's go with intellectually- rather than emotionally-sad, then.
Though I totally understand the reasons—IP usage rights and quality control chiefly, I assume—it's a shame BoC's back catalogue isn't more readily available. But Gods-bless the internet that it's (somewhat) available at all.
So much to choose from here, but let's go with Forest Moon from A Few Old Tunes. Lovely lovely tune. Doesn't fart about. Straightforward. Some synths and percussive elements come and go, but that's about it. Tempted to digress into their lovely track titles here, but let's save it.
Tough one. Many contenders. Let's go with Cold Earth. We're back in banger territory: it's the best track on Tomorrow's Harvest. High praise.
I've said in the past that BoC melodies somehow seem more like geological finds than compositions. Primal. Woven into the fabric of space. This is one of those.
Why happy? The tune, and the bassline in particular, resolves itself satisfyingly, and every few bars. I think it might induce just a little bit of dopamine. Glorious.
Least favourite: good words. BoC haven't done anything bad in my view. But Dayvan Cowboy is an easy choice. May be the only BoC recording with an official video, which says it all.
The album it belongs to, The Campfire Headphase, is BoC at their most coffee table (despite sublime moments like Peacock Tail, Oscar See Through Red Eye and Ataronchronon). There's nothing wrong with it. It's an accessible way in. I'd probably put it on a mixtape for BoC beginners. But it's nowhere near the advanced-listening curriculum.