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
Bass Line Composer
Yo, Bass drummers! Got a split in your head that you've just got to hear right now? Got a line or a lick or an exercise to put down? Compose it and play along with the new Bass Line Composer App!
$1.99 · In-app purchases
PRICE
$1.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 4.7
181 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 should your app do differently? Your note travels with the kit so your coding agent builds around your idea.
What's included18 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 Bass Line Composer: 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
Add advanced editing tools like effects and mixing options.
Assumption to check: Limited note editing features compared to full DAWs.
Validate with people who use this workflow before building.
Hypothesis 2
Incorporate sharing options for created bass lines.
Assumption to check: Lack of social sharing features.
Validate with people who use this workflow before building.
Hypothesis 3
Enable real-time collaboration for users to work together.
Assumption to check: No collaboration tools for multiple users.
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
Yo, Bass drummers! Got a split in your head that you've just got to hear right now? Got a line or a lick or an exercise to put down? Compose it and play along with the new Bass Line Composer App! Now you’ve got a whole bass drum line to play along with. Practice splits and interp. Write out your exercises or make up new ones. Put down that new street beat that’s been bouncing around your brain. Speed it up, slow it down, try it out, edit it, and max it out! Compose and play along with the actual bass drum sounds of the Paul Rennick 2012 Santa Clara Vanguard, as recorded by bass tech Brian Lowe - tuned the way they’ll sound on finals night. Best used with Headphones About Telephonic Amusements: Nicholas Wheeler, software engineer, marched Sky Ryders, VK, and UNT - taught at Pioneer and UNT; David Croy, designer, marched Sky Ryders and tech’ed under Paul Rennick at Sky, VK, and has provided visual consulting for UNT and Dynasty Drums.
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
Zustand
@react-navigation/native
expo-av
react-native-gesture-handler
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.
