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.
This harmony singing app comes with three songs, with 50 more available through in-app purchase
$1.99 · In-app purchases
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.
A product spec, screen plans, and build steps for your coding agent.
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Combine features and design from your favorite apps.
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What should your app do differently? Your note travels with the kit so your coding agent builds around your idea.
A product spec, phased build plan, differentiation notes, and screen references.
Illustrative example: an invoice app for independent contractors. Your kit is tailored to the app you choose; this is not its generated content.
Goal: Send a clear invoice after finishing a job.
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.
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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Good fit for mobile-first iOS and Android prototypes with managed app scaffolding.
Rork plan preview for Sing Harmonies: 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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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
Assumption to check: Limited song selection compared to competitors
Validate with people who use this workflow before building.
Hypothesis 2
Assumption to check: User interface can feel outdated
Validate with people who use this workflow before building.
Hypothesis 3
Assumption to check: Audio playback quality can vary
Validate with people who use this workflow before building.
Hypothesis 4
Assumption to check: In-app purchases can be confusing
Validate with people who use this workflow before building.
Original App Store material. Ratings and screenshots describe the existing app, not proof of demand for your version.
This harmony singing app comes with three songs, with 50 more available through in-app purchase. Learn how to sing harmony and polish your harmonizing skills by playing or muting any of the singers as you sing along with 4-part vocal arrangements of "Lean On Me", "Teach Your Children", and "Proud Mary". Harmonizing is easy with this multi-track learning app. "Great for vocalists who have difficulty hearing or singing harmonies." https://makingmusicmag.com/8-spectacular-apps-for-singers/ The 50 additional songs available through in-app purchase include "Hallelujah", "Amazing Grace", “Sound of Silence”, “Take Me Home, Country Roads”, "Shallow", "Seven Bridges Road”, “Let it Be”, and many more. Detailed song info is at https://singharmonies.com/. "One of the best iPad apps for singers.” https://www.apppicker.com/applists/2488/the-best-ipad-apps-for-singers DETAILS • No music reading, previous singing experience, or training necessary. • Support, song info, harmonizing tips and more can be found at https://www.singharmonies.com. • The vocal harmony arrangements range from easy to challenging. Vocal arrangements, difficulty level, and keys are on the song info page at https://www.singharmonies.com/song-info. • Works with iPhone, iPod Touch, and iPad with iOS 9 and later. • All ages can use. • Please note that the app cannot be used with songs in other music libraries on your device. HOW TO USE • Tap ‘play’ to hear a 4-part harmony version of the song. Tap any singer to rotate through the three volume settings: full, soft, and silent. Tap the band in the background to turn the music track on or off. • To hear and learn any of the parts, mute the three other singers and sing along with the solo voice, with or without the music track. Then tap any or all of the other singers and sing your part along with them. • The voices can be added or muted as the song progresses, and can be played at half volume as a guide while the other voices are set at full volume. • Move to different parts of the song with the slider at the bottom of the screen. • Tap the menu icon to navigate to other areas of the app. Tap My Library to view and select any the songs you can currently play. Tap Song Store to see available songs and to purchase more songs. Tap More Info for instructions and support.
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Plan a focused first version with your coding agent. These are planning assumptions, not a delivery guarantee.
Choose one audience and one core workflow. Use the kit to agree on its screens, data, and acceptance criteria before building.
Decide which secondary features, integrations, and platform support can wait. Your version does not need to reproduce everything in the original.
Validate external services, specialist technology, data access, and ongoing costs for your chosen scope.
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.