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
Appcompanist: Vocal Training
Appcompanist gives singers, voice teachers, choral directors, and choirs full musical control over thousands of professional piano accompaniments.
Free · In-app purchases
PRICE
Free
In-app purchases
BUSINESS MODEL
Freemium
No overall Grossing estimate available
RATING
★ 4.6
257 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 included20 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 Appcompanist: Vocal Training: 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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App evidence
Original App Store material. Ratings and screenshots describe the existing app, not proof of demand for your version.
Screenshots
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App Store description
Appcompanist gives singers, voice teachers, choral directors, and choirs full musical control over thousands of professional piano accompaniments. Practice, teach, rehearse, and perform with flexible accompaniment you can actually control in real time. Change key instantly, control tempo during play, blend melody in or out, hold fermatas, check pitches, and save your own tempo and fermata changes as Custom Versions. The free version includes over 1,000 Vocal Exercises and 75 complete piano accompaniments with full app functionality. The growing Appcompanist library includes thousands of flexible piano accompaniments for opera arias, art songs, musical theater solos, jazz standards, pop and rock songs, choral music, complete works, and more. New recordings are added regularly, including user-requested repertoire. Why singers, teachers, and choirs use Appcompanist: • Instantly transpose any accompaniment to the key that fits your voice best. • Control tempo during play to create ritardandos, accelerandos, rubato, and more. • Use the patented Fermata Button to hold notes, chords, and pauses, then re-enter in perfect sync with the piano. • Turn the melody guide on or off at any time during play, choose from three octaves, and adjust the melody level against the accompaniment. • Check the next melody pitch when stopped and time entrances with confidence. • Save your tempo and fermata changes to create Custom Versions that can still be controlled during playback. • Learn choral and ensemble music more easily by emphasizing one or more voice parts against the accompaniment or against other parts. • Add markers, cuts, and loops for easier navigation, teaching, rehearsal, and focused practice. • Repeat vocal exercises up, down, or in the same key. • Create video recordings while using Appcompanist playback tools. • Search, filter, and sort the library to quickly find the right piece. Subscription options: Note: Prices shown are in US dollars. In-app pricing in other countries may vary based on current exchange rates. Contemporary Voice Collection US $9.99/month or US $99.99/year
Written user reviews are not shown here. Check current App Store reviews >
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
Provide a more robust offline mode with full access to downloaded content.
Assumption to check: Limited offline functionality and features.
Validate with people who use this workflow before building.
Hypothesis 2
Create a clearer subscription model with guided prompts.
Assumption to check: In-app purchases can be confusing.
Validate with people who use this workflow before building.
Hypothesis 3
Implement an AI-driven recommendation system based on user behavior.
Assumption to check: Not enough personalized recommendations.
Validate with people who use this workflow before building.
Hypothesis 4
Ensure higher audio quality streaming options and settings.
Assumption to check: Audio quality issues in streaming.
Validate with people who use this workflow before building.
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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Zustand
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expo-av
BUILD KIT DIFFICULTY
Expert
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.
