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.
App Overview
Audio Frequency Converter
The Audio Frequency Converter is a small but powerful app for converting music to 432Hz, 528Hz, and custom frequencies.
$8.99 · In-app purchases
PRICE
$8.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 3.7
10 ratings · Top 50%
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.
Build your own version
Build Kit
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A product spec, screen plans, and build steps for your coding agent.
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What's included14 files
A product spec, phased build plan, differentiation notes, and screen references.
- START_HERE
- AGENTS
- EVIDENCE
- SPEC
- BUILD_PLAN
- DIFFERENTIATION
- skills/
- screens/
Preview a sample Build Kit No email needed
Illustrative example: an invoice app for independent contractors. Your kit is tailored to the app you choose; this is not its generated content.
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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Free quick prompt For a smaller starting point
Quick prompt
Good fit for mobile-first iOS and Android prototypes with managed app scaffolding.
// RORK SYSTEM PROMPT
Rork plan preview for Audio Frequency Converter: 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 to include more audio frequency units and formats.
Assumption to check: Limited conversion options compared to competitors.
Validate with people who use this workflow before building.
Hypothesis 2
Provide detailed information or examples of conversions.
Assumption to check: Lack of user feedback on conversion accuracy.
Validate with people who use this workflow before building.
Hypothesis 3
Implement offline capabilities for users without internet.
Assumption to check: No offline functionality for frequency conversion.
Validate with people who use this workflow before building.
Hypothesis 4
Simplify the in-app purchase flow and provide a better onboarding experience.
Assumption to check: In-app purchase process is not user-friendly.
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
The Audio Frequency Converter is a small but powerful app for converting music to 432Hz, 528Hz, and custom frequencies. Please contact us if you have questions: https://www.tequnique.com/contact ## Features - Load mp3, wav, m4a (AAC), FLAC, and many other file formats. - Supports 24 bit high quality audio (for instance FLAC) input and output. - Support for multi-channel (more than two stereo channels) audio. - Export converted music to mp3, m4a, FLAC, wav, or the input source format. - Built-in default frequencies: 174Hz, 285Hz, 396Hz, 417Hz, 432Hz, 440Hz, 444Hz, 528Hz, 639Hz, 741Hz, 852Hz, 963Hz. - Convert to different custom frequencies (up to two decimals). - Define the source and target frequencies. ## Use cases Example use-cases for the app (but no limited to): - Music therapy. - Esoteric applications (e.g. Solfeggio). - 432Hz music listening. - 528Hz music listening. - Music tuning: Many musicians do not use 440Hz as base frequency. Also classic orchestras usually use their own base frequencies. The app allows you to adjust your music to these frequencies. - Well-being and joyfulness.
Written user reviews are not shown here. Check current App Store reviews >
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.
SUGGESTED BUILD STACK
React Native
Expo
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BUILD KIT DIFFICULTY
Intermediate
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.
