Rubbery Intro Patch:
I like the touch of attack at the start of the sound. Not sure if it's two layered patches or stacked oscillators, but there's a cool de-tune/spread that gives it some extra space. The hint of crunch on it helps to give it character as well.
Intro Sub Bass:
Sounds like a fairly simple sine wave sub which fits hip-hop perfectly. Maybe a bit of side-chain or slower attack to roll off some of the clicking. I could be tripping, but I don't think it's in mono - which would also give it a bit more weight by being centred in the mix.
Plucky Clavinet Sound (0:22):
Not sure if you were going for a Clavinet sound, but if you were, you nailed it. Maybe a bit of filter/wah to give it some extra funk. Chorus and drive for that punchy Stevie Wonder sound. Otherwise, pretty dope. I've never used Serum, but is there a way to lower the voice polyphony? Classic Clav's have limited polyphony so you end up with voice stealing which actually adds some cool character and forcing that bouncy alternating styled rhythm you hear in 70s sould/funk/disco. In this particular use, it'd function kinda like a choke group and effectively cut the sustained ring of the notes down. Possibly could add some rhythmic character. Just an idea.
Sliding Whale Call (0:40):
This is my favourite sound in the track. The way the attack and glide moves along with the pitch - and the beautiful line you wrote - this adds TONS of depth and atmosphere. I think the reason I like so much is because of how well it blends (more on that later). I mean this in the best way possible...It's one of those pretty Sega/Super Street fighter type counter melodies. I think there's a slow moving arpeggio of some sort on top of it? Can't really make it out (again, if there is another element here, great work on blending it in!)
8-Bit Horns (0:44):
This is the patch that could benefit from add layers of polyphony! Again, by 8-Bit Sega sounding, I only mean it as a compliment. This is also another beautifully written melody that serves as a great response to the "call" melody of the patch above. Great sound, maybe a bit prouder in the mix would let it shine more. Alternatively, I'd bring down the "Rubbery" patch a bit and at the very least let the saccharine melodies of this part shine.
My main piece of feedback for this piece, and it's associated patches, is that the elements don't blend together that well. It sounds like layers stacked on top of each other. Which is a shame, because some of the lines are really quite beautiful and have really allow the melodic themes to flow from one patch to another. I feel like some small things like reverbs, strategic EQs, voice polyphony and prominence in the mix would allow each element to shine. As it is, the piece just sounds a bit too flat.
Now, I do think these are all really cool patches, that could be used individually, in other tunes to great affect. Apologies for the silly patch names, I'm just trying to find uniquely analogous terms so you know which one I'm referencing. You're a better man than me making patches from scratch lol.