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
Nashville Numbers
Music notation is made simple with this shorthand system which puts chords into numbers 1 though 7 and streamlines the page into a simple and clean format
$9.99 · In-app purchases
PRICE
$9.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 4.5
102 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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Build Kit
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A product spec, screen plans, and build steps for your coding agent.
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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/
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 Nashville Numbers: 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 chord database and offer more genres.
Assumption to check: Limited chord library compared to competitor apps
Validate with people who use this workflow before building.
Hypothesis 2
Integrate social sharing options for users to share their charts.
Assumption to check: Lack of social sharing features
Validate with people who use this workflow before building.
Hypothesis 3
Implement offline functionality for saved charts.
Assumption to check: No offline access to chord charts
Validate with people who use this workflow before building.
Hypothesis 4
Redesign navigation for improved user experience.
Assumption to check: User reviews mention difficulty in navigation
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
Music notation is made simple with this shorthand system which puts chords into numbers 1 though 7 and streamlines the page into a simple and clean format. Forget about pencil, erasers and photocopy! This app combines technology with tried and tested methods; allowing users to create song charts with the ease and speed of pen and paper. For over 60 years, the Nashville Number System has been the standard for musicians in live performance, recording sessions, and teaching environments. The published book has become required reading in many of the most prestigious music schools, including Belmont, ETSU, Lee and Liberty University, while also being required reading for anyone when they get their first gig in music city. This innovative app brings the must-read instructional book by Chas Williams, with well over 50,000 copies sold, into our digital age by seamlessly allowing charts to be written on your digital device! Please give feedback of a 5 star review, or contact us directly. If you’re not happy with the app, we will issue a full refund of your purchase price (in exchange for not writing a bad review) and insure your issues are reviewed and fixed. You can keep your version and be notified when an update has been made. Thank you for your business. My name is Leland and I’m on the development team along with Chas. My personal email is [email protected] so you can contact me with issues or great musical stories! Chart Everything My Friends!!!
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
react-navigation
expo-sqlite
react-native-reanimated
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.
