App Overview

WorldScales icon

WorldScales

Kelfar Technologies · Music

Not all scales are created equal

$19.99 · In-app purchases

PRICE
$19.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
4.7
21 ratings · Top 15%

Evidence scope: No current overall US chart position is available. Category-chart positions shown in discovery are a separate scope. Revenue is a directional model estimate, not verified earnings.

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What's included17 files

A product spec, phased build plan, differentiation notes, and screen references.

  • START_HERE
  • AGENTS
  • EVIDENCE
  • SPEC
  • BUILD_PLAN
  • DIFFERENTIATION
  • skills/
  • screens/
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Illustrative example: an invoice app for independent contractors. Your kit is tailored to the app you choose; this is not its generated content.

Feature spec

Goal: Send a clear invoice after finishing a job.

  • Add a client, line items, a due date, and payment instructions.
  • Preview the total before exporting a PDF.
  • Keep an editable draft if export fails.

Screen plan

Invoice editor: Client at the top, editable line items in the middle, total and preview action at the bottom.

States: Empty draft, validation errors beside each field, exporting, and a retry action that preserves the draft.

Differentiate and validate

Hypothesis: Contractors need faster repeat invoices more than more templates.

First experiment: Test duplicating a previous job with five contractors. Watch where they hesitate before expanding the feature set.

The full kit adds a phased build plan, evidence notes, tool prompts, and implementation guidance. It is a plan for your coding agent, not a finished app.

Usage: Mechanics are fair game; never reuse the original name, branding, assets, or verbatim copy.

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Quick prompt

> SELECT BUILD PLATFORM:

Good fit for mobile-first iOS and Android prototypes with managed app scaffolding.

// RORK SYSTEM PROMPT
Rork plan preview for WorldScales: map the core Music workflow, choose the smallest differentiated feature set, define the data and monetization boundaries, then prototype the riskiest user journey first.
            

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Opportunities

AI-GENERATED OPPORTUNITY HYPOTHESES

These are generated suggestions, not verified review quotations. Check current App Store reviews and speak with users before treating a possible gap as a requirement.

Hypothesis 1

Expand the scale library and provide user-generated content.

Assumption to check: Limited scale variety compared to competitors

Validate with people who use this workflow before building.

Hypothesis 2

Implement offline access for downloaded scales.

Assumption to check: No offline access to scales

Validate with people who use this workflow before building.

Hypothesis 3

Introduce social sharing options for scales.

Assumption to check: Lacks social sharing features

Validate with people who use this workflow before building.

Hypothesis 4

Introduce a freemium model with basic scales available for free.

Assumption to check: Pricing may be high for casual users

Validate with people who use this workflow before building.

App evidence

Original App Store material. Ratings and screenshots describe the existing app, not proof of demand for your version.

App Store description

Not all scales are created equal. This app allows you to break out of the limitations of equal-tempered scales and gives you freedom to tune the built-in keyboard in whatever way you want. Loaded with many presets and samples you can explore ancient scales, byzantine music, oriental vibes or configure your own scales. Have you ever wondered why we tune our instruments the way we do? They are usually tuned to an "equal-tempered scale", which divides the octave into equally spaced tones and semitones. This has become the most prevalent way of tuning the instruments in the west since the 18th Century. Today, musicians use this tuning system, and the scales based on it, without ever considering other ways. For example, in the Middle Ages European musicians generally used Pythagorean tuning, and today many traditional instruments in the Middle East and Asia are tuned according to regional systems and standards. Included features: ● Ability to tune each key in the octave individually (+- 100 cents). ● 35> High quality sampled instruments: From grand piano, violin and organ to oriental oud and kanun, to voices of a choir singing Ison voices. Many samples are polyphonic and have multiple velocity layers. ● MIDI In. Connect your External MIDI keyboard and play microtonal music. Tuning the individual keys is normally only possible on $1000+ keyboard! ● Many presets introducing lesser known western, byzantine and oriental scales. ● Ability to save your own scales and tunings. ● Entering directly frequency ratios, frequencies or cents. ● Shows on the piano keys where the scale starts and what keys are included in the scale. ● Changing the root key of a scale: all tuned keys are shifted correctly. ● Audio effects: reverb and compressor. ● And more…

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Screenshots

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Build scope

Plan a focused first version with your coding agent. These are planning assumptions, not a delivery guarantee.

Define the first version

Choose one audience and one core workflow. Use the kit to agree on its screens, data, and acceptance criteria before building.

Set boundaries

Decide which secondary features, integrations, and platform support can wait. Your version does not need to reproduce everything in the original.

Check the hard parts

Validate external services, specialist technology, data access, and ongoing costs for your chosen scope.

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BUILD KIT DIFFICULTY
Advanced

From the Build Kit assessment.

A reliable timeline needs an agreed scope and a technical check. Ask your agent to estimate the phases in BUILD_PLAN.md after that review.