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
Realbook Master
The sheet music app that understands real live musicians.
$9.99 · In-app purchases
PRICE
$9.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
N/A
No ratings yet
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/
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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.
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 Realbook Master: 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 library with user-generated content and partnerships.
Assumption to check: Limited music sheet options available compared to competitors.
Validate with people who use this workflow before building.
Hypothesis 2
Implement offline downloads for purchased tracks.
Assumption to check: No offline playback feature.
Validate with people who use this workflow before building.
Hypothesis 3
Include options to share tracks on social media.
Assumption to check: Lack of social sharing features.
Validate with people who use this workflow before building.
Hypothesis 4
Add built-in practice tools to enhance user experience.
Assumption to check: No practice tools like metronome or tuner.
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 sheet music app that understands real live musicians. Swipe up or down to change keys on the fly - because the show MUST GO ON! Built for any musicians who perform live. Whether you're on stage, in rehearsal, or playing at church, Realbook Master gives you the instant freedom. Features : 1) Transpose chords and melodies to all 12 keys by swiping the sheet music or using +/- buttons in the top toolbar 2) Download sheet music from the forum 3) Lyrics On/Off 4) Select transposing instruments (bass clef support) 5) Create and share setlists 6) Export transposed sheet music as PDF 7) MusicXML file support 8) Supports various themes, music fonts, and background modes Perfect for: - Jazz musicians who need quick key changes - Wind players tired of transposing manually - Church musicians managing large song libraries - Bassists who need proper clef and range - Any performer who values speed and flexibility on stage
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 Navigation
Expo AV
Zustand
Expo File System
React Native Reanimated
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.
