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Tech / Season 2 / EP01

AI Music Generation

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Shez

Making music is hard.

Shez

That's... a legitimate banger.

Shez

Kurumi! How? It's not just a melody. It has layers. It sounds... produced.

Kurumi

Music AI is an efficient piece of signal processing. It can generate music faster than you can listen to it.

Kurumi

Because it is. But not the way you think.

Kurumi

It's not an automated band in a studio. It's more like a single machine painting.

Shez

Painting? It's a sound I'm hearing.

Kurumi

Your prompt goes to an LLM. It generates thematic lyrics and tags like `[Verse]` and `[Chorus]`.

Kurumi

The lyrics and style tags are converted into a set of abstract mathematical tokens. A tiny map that encodes the overall vibe and flow.

Shez

Okay, but how does it handle all the instruments?

Kurumi

This is the clever cheat code. Instead of building up every instrument or stem, it generates a *single* mel-spectrogram. The full, finished picture of the whole song, all at once.

Shez

Just one?

Kurumi

Yup. No multi-track recorder, no separate diffusion magic for drums or vocals. It's more like a futuristic flatbed scanner for music.

Kurumi

The model starts with noise and sharpens it, one pass, using the blueprint as guidance. Everything—the kick, the pad, the harmonies—gets painted in at once.

Shez

Okay, so it's one big picture. How do you turn it into sound?

Kurumi

The whole spectrogram goes through a neural vocoder pass, something like EnCodec or HiFi-GAN. No fancy mixdowns, no per-instrument rendering.

Shez

Hold on. If everything is baked into one spectrogram and vocoded in a single pass… shouldn't it sound like mud? Kick drum fighting the bass, vocals drowning in reverb. How does it still sound so good?

Kurumi

It should. And with 2022 models it did. But 2025 models are scary good for one simple reason…

Kurumi

Look here — see how the bass energy dips exactly where the kick hits? See the 3–5 kHz notch when the vocal comes in? That's not a mixing engineer. That's the U-Net hallucinating negative space.

Kurumi

But you are right that this architecture can't produce sounds that are perfect. Artifacts sneak in from 'spectral peaks.' That's how AI-generated songs get detected.

Kurumi

We call these spectral peaks or diffusion artifacts. They're leftover deconvolution errors from the denoising steps. Human ears hear them as a subtle metallic sheen, glassy, or 'sparkly' quality — especially on hi-hats, vocal sibilance, and reverb tails.

Kurumi

A real reverb tail decays chaotically. An AI tail decays in perfect little steps because the model was denoising in fixed iterations. Your brain notices the grid pattern even if you can't consciously hear it.

Shez

That's creepy. It's like hearing the pixel grid in audio.

Kurumi

But who knows what happens in a year or two. The artifacts are getting smaller every model release. One day even golden ears won't be able to tell.

Shez

So... Music AI isn't an artist or an orchestra. It's a compression wizard.

Shez

But is it... creative?

Shez

Wait a sec.

Shez

I work with cloud budgets. GPUs aren't free. Neither is bandwidth for audio.

Shez

And all this is just to let me mess around with rap prompts that tricks it to say the N-word for free? How is Suno still profitable?

Kurumi

It would be, if they weren't obsessed with optimizing. They attack the three cost monsters: **Compute**, **Storage**, and **Bandwidth**.

Shez

Okay, break down Compute. How do they make it not outrageously expensive?

Kurumi

Latent space. They compose and diffuse in a tiny, compressed version of the song—a thumbnail, not a mural.

Kurumi

If they tried to generate the final, detailed waveform directly, it would eat their GPU bill alive. Diffusing in the latent space means the hard part happens fast, small, and cheap. Scaling up with a vocoder is quick and efficient.

Shez

They shrink the work. But storage? Every song must add up fast.

Shez

It just deletes it?!

Kurumi

It deletes the *audio*, but it keeps the *recipe*. The original prompt and the latent tokens—the tiny thumbnail sketch from before. That's only a few kilobytes of text.

Kurumi

If you come back a week later and want to play it, the system just re-generates it on the fly from that recipe. A little bit of GPU cost is cheaper than paying to store a million abandoned songs forever.

Shez

That's brutal. What about bandwidth for playback?

Kurumi

The final trick: streaming. They use the most compressed audio codec they can get away with.

Kurumi

Not MP3, not WAV. They use **Opus**, the same thing Discord uses for voice. They can stream a song to you using a fraction of the data.

Kurumi

So: They compute on a tiny version of the song. They delete the full version if it's not popular. And they vacuum-seal the data before they send it to you.

Shez

I can't believe engineers sometimes can be more creative than artists!