Cassette Video SFX Review: Automatic Sound for Video, No Prompt

Cassette Video SFX is a model that adds sound to video automatically. You upload a silent clip, it analyzes what is happening on screen and generates a matching soundtrack. No prompt, no settings. In the WebTerra AI catalog it is the most affordable way to add sound to a video. In this Cassette Video SFX review we explain how it works, Cassette Video SFX pricing, how to use it online and when you should pick a different model instead.

Anyone working with AI video generators knows the “silent clip” problem. Many video models produce great visuals with no audio, and a silent clip in a social feed feels unfinished. Hunting for effects in sound libraries, lining them up frame by frame and mixing tracks takes time. Cassette Video SFX takes that routine off your plate: one click, and the clip has sound.

The model comes from Cassette AI, a team working on generative audio. Its Video SFX model is built for one simple job: add sound to a video quickly and cheaply, without asking the user for a description or any sound design skills.

What Cassette Video SFX can do

The model works in video → audio mode. Your clip goes in, and the same clip with generated sound comes out.

• Fully automatic. No need to describe the sounds you want — the model works it out from the content of the frame.
• Lowest price in its category. The service catalog labels Cassette Video SFX as the cheapest option for adding sound to video.
• Minimal steps. Upload, run, download — no presets or parameters to tweak.
• Built for batches. When you need to add sound to many short clips, skipping the prompt saves time on every single one.

It helps to understand the model’s logic: it does not know your intent, it only sees the picture. Waves on screen mean ocean sounds; a car means engine noise. So the more obvious the sound source in the video, the better the result. When you need something specific that is not visible in the frame, choose a model that accepts a text description (see the comparison section).

Cassette Video SFX specs

Parameter	Value
Developer	Cassette AI
Type	Sound for video (SFX)
Input	Video → audio
Prompt	Not required, fully automatic
Price per generation	29–33 credits for 5 seconds of video (about $0.34–0.42)

How to use Cassette Video SFX in WebTerra AI

1. Sign up — you get 60 free credits, enough for a first test.
2. Prepare your clip: your own footage or a clip generated by any video model in the service.
3. Open the sound for video page in your dashboard and select Cassette Video SFX.
4. Upload the video.
5. Check the cost and start the generation — there is nothing to describe.
6. Review the result and download the clip with sound.
7. If the sound misses the mood, try again or switch to a prompt-based model.

Video models that pair well with Cassette are collected on the AI video generation page.

Cassette Video SFX pricing

The cost depends on the length of the clip. Here is the price for a 5-second video on each plan.

Plan	Credits for 5 s	Price in USD
Starter	33	about $0.42
Pro	31	about $0.37
Ultra	29	about $0.34

The 60 free credits cover one 5-second clip on the Starter plan, with some left over for other experiments, such as a few images. That is enough to see how the model handles your type of content. Credit packs and discounts are on the pricing page.

Because the price depends on duration, trim your clip to its final length before adding sound — you will not pay for seconds that end up on the cutting-room floor anyway.

Examples: clips that work well

Cassette Video SFX needs no prompt, but sound quality depends on what is happening on screen. Below are prompts for video models that produce clips with clear sound sources. Generate a video from one of them, then add sound with Cassette.

Rocky shore

Waves crashing on a rocky shore at sunset, seagulls flying overhead, slow camera pan, cinematic

Waves and birds are obvious sound sources, so the model “hears” the scene easily.

City street

Busy city street on a rainy evening, cars passing with headlights, people with umbrellas walking, reflections on wet asphalt

Rain, traffic and footsteps — a layered backdrop for an atmospheric clip.

Kitchen

Close-up of vegetables being chopped on a wooden board, then tossed into a sizzling pan, steam rising, warm kitchen light

Knife taps and sizzling — a food-content classic for Reels.

Cozy fireplace

Fireplace with crackling logs in a cozy cabin, snow falling outside the window, slow push-in

Crackling fire — a calm backdrop for seasonal posts.

Action sports

Skateboarder riding down a concrete ramp and landing a jump, wheels rolling on the surface, sunny skatepark

Dynamic sounds of movement and landing.

Forest stream

Forest stream flowing over mossy stones, sunlight through the leaves, birds in the trees, gentle camera movement

Water and birdsong — a perfect soundscape for relaxing content.

Tips for better sound

Make the sound source visible

The model goes by what it sees. If the main sound source is tiny in the background, it may be ignored. Shots where the sound-making object fills a noticeable part of the frame come out more accurate.

One scene per clip

Videos that jump between locations are harder to score coherently. If your edit has several scenes, process each one separately and then assemble them.

Trim before you add sound

Extra seconds cost credits. Edit first, add sound second.

Leave room for voice and music

Cassette creates effects and ambience. Add voiceover and music as separate tracks — they are easier to balance that way.

Test on short samples

Before processing a whole series, try the model on one or two clips typical of your content. If you like the result, you can then work through the rest in bulk.

Workflow: from silent clip to finished video

Cassette shines as one link in a chain. Here is what a full cycle can look like inside a single WebTerra AI dashboard:

1. Visuals. Generate a clip from text with a video model, or animate a photo in image-to-video mode.
2. Edit. Trim the excess so you do not pay for unneeded seconds in later steps.
3. Effects and ambience. Run the clip through Cassette Video SFX to get background sound that matches the frame.
4. Voice. If you need narration, generate it separately with a TTS model such as ElevenLabs Multilingual.
5. Music. Optionally add a music bed — for example with Sonilo Music 1.1, which fits music to the edit of your clip.
6. Mix. In any video editor, balance the levels: voice loudest, effects lower, music in the background.

This approach keeps you flexible: each layer can be regenerated on its own without touching the others. And because Cassette is the cheapest step, it lets you check quickly whether a clip “works” with sound before you invest in voice and music.

Who Cassette Video SFX is for

• AI video creators. Quickly bring silent clips from video models that do not generate sound to life.
• Social media. Reels, Shorts and Stories that need background sound instead of silence.
• Marketplaces and ads. Short product videos with atmospheric sound at minimal cost.
• Content studios. Large batches of short videos where speed and low unit cost matter.
• Beginners. Anyone who does not want to deal with sound prompts or effects libraries.

Cassette Video SFX vs other video sound models

WebTerra AI offers several models that add sound to video. Cassette is the simplest and cheapest; the others give you more control.

Model	Key feature	When to choose it
Cassette Video SFX	Automatic, no prompt	You need sound fast and at the lowest price
MMAudio V2	Sound for video from a prompt	You want to tell the model what should be heard
Hunyuan Video Foley	Cinematic foley	You need a detailed, film-style soundscape
Mirelo SFX 1.6	Synced SFX up to 60 s	Longer clips with precise sync
PixVerse Sound Effects	SFX plus background music	You need effects and music together
ThinkSound	Sound that fits the scene	The sound should follow the story of the scene
Sonilo SFX 1.1	SFX with a commercial license	The video is for commercial use
Kling Video to Audio	Sound from a prompt, up to 20 s	Text control for short clips

If you want control over what is heard, read our MMAudio V2 review — there the sound is defined by text. For films and promos with rich foley there is Hunyuan Video Foley, and for longer clips with tight sync, Mirelo SFX 1.6. When you need music alongside effects, consider PixVerse Sound Effects. Cassette wins wherever speed, simplicity and price come first.

A practical rule of thumb: use Cassette for drafts, tests and high-volume content; for the final version of an important video, compare its output with one of the models that offer more control. And if the video will be used commercially, note that Sonilo SFX 1.1 comes with a commercial license.

Cassette Video SFX limitations

• No prompt. You cannot tell the model which sounds you want. If specifics matter, pick a prompt-based model.
• Sound from visuals only. Off-screen events or story-driven sounds will not be generated.
• Not a replacement for voice or music. Use separate models for narration and a music bed.
• Price depends on duration. A longer clip costs proportionally more.
• Results vary. Sometimes it is worth generating twice and keeping the better take.

FAQ

Do I need to write anything to generate sound?

No. Cassette Video SFX is fully automatic — just upload the video.

How much does it cost to add sound to a clip?

5 seconds of video costs 33 credits on Starter (about $0.42), 31 on Pro (about $0.37) and 29 on Ultra (about $0.34).

Are the free credits enough?

Yes, 60 credits cover one 5-second clip on any plan.

Does the model add music or voice?

It creates sound based on the content of the frame — effects and ambience. Use separate models for music and voiceover.

How is Cassette different from MMAudio V2?

Cassette needs no description and costs the least. MMAudio V2 lets you define the sound with text, giving you more control.

Can I add sound to a video made by another model?

Yes — that is exactly where it is most useful: generate a clip with any video model, then add sound with Cassette.

Cassette Video SFX is the easiest way to get rid of silent video: no prompts, no sound libraries, and well under half a dollar for 5 seconds. Upload your clip and add sound in WebTerra AI now.