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
Retro Keys: Piano, Wurl, Rhds
RETRO KEYS: 4 VINTAGE KEYBOARDS IN ONE
$7.99 · In-app purchases
PRICE
$7.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 4.9
193 ratings · Top 5%
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 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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Quick prompt
Good fit for mobile-first iOS and Android prototypes with managed app scaffolding.
// RORK SYSTEM PROMPT
Rork plan preview for Retro Keys: Piano, Wurl, Rhds: 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
Provide more free sounds or features to engage users.
Assumption to check: Limited free trial sounds
Validate with people who use this workflow before building.
Hypothesis 2
Clarify in-app purchase options and benefits.
Assumption to check: In-app purchase confusion
Validate with people who use this workflow before building.
Hypothesis 3
Introduce collaborative features for users to share and create together.
Assumption to check: No collaboration features
Validate with people who use this workflow before building.
Hypothesis 4
Optimize audio playback for better performance.
Assumption to check: Occasional audio latency
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
RETRO KEYS: 4 VINTAGE KEYBOARDS IN ONE Warm, soulful keyboard sounds with real tape character. RETRO KEYS gives you four classic instruments in one app: RHDS STAGE 73, WURL ’78, CP Electric Grand, and RETRO PIANO. Recorded to analog tape by a GRAMMY-nominated engineer. Then blended with physical modeling for a responsive, inspiring feel. From polished to dusty and worn-in, these sounds are full of vibe. You get rich vintage tone without the giant download. The full app is only around 150 MB! (For all 200+ Presets & 4 Instruments Total) Perfect for Lo-Fi, Indie, Worship, Hip Hop, Rock, Cinematic, Soul, Pop, Jazz, Ambient Textures, and Singer-Songwriter production. Premium App: One time purchase. No ads, subscriptions, or in-app purchases, Everything Included! "This thing is Incredible!" - Jade Starr “Blown Away! Incredible quality. Makes me feel like I'm sitting in front of an old keyboard” - Brian Kupferschmid, All Things VST "I haven't had this much FUN with any other electric piano app on iOS!" - Luxthor "I have the MODX and the STAGE 73 is better in this app" - Loopy Pro forum "The warble is Gold! And the CP80 sounds incredible. So rich and warm." - Seljoy Youtube Channel WATCH VIDEOS & HEAR: audiokitpro.com/retrokeys ANALOG SAMPLES + PHYSICAL MODELING Sounds like a record. And only 150MB for all 4 instruments! NOTE: Does not work well on 2015 iPad Air 2 and earlier devices FEATURES • 4 Vintage Keyboard instruments in one app • Old Soul. New Sounds. • 200+ presets by Moby Pixel, Analog Matthew, Doug (The Sound Test Room) & more • Real Samples blended with physical modeling • Tape-style 8-Track Double Tracking • Big sound. Tiny footprint (Less than 150mb) • Hi-fi to Lo-Fi tones • Easy to Use and Shape Sounds • Aftertouch can affect any control • MIDI keyboard and sustain pedal support • Selectable Noise (Tape, Vinyl, etc) • AUv3 plug-in support • Universal app for iPhone and iPad • Instrument Key Release Sounds • Record Button to record your ideas. Quickly sample & export! “The Best Sounding Electric Keys you can get at this Price!” — Producer Jay Zen "Sounds full, lush and warm. One of the best sounding, premium apps on iOS and for an amazing price" — April Rox Studios WORKS BY ITSELF • Play instantly on iPhone or iPad. • Connect a MIDI keyboard with Aftertouch for an expressive experience. • Plus, MIDI Learn for all parameters. WORKS AS A PLUG-IN Use RETRO KEYS as an AUv3 instrument in Logic for iPad, GarageBand, AUM, Cubasis, and more. Includes 220+ presets by Moby Pixel, Analog Matthew, Doug Woods, Bri Kup, DMT Cymatics, Red Sky Lullaby, Joe Zeno, and more. Use RETRO KEYS standalone or inside your favorite AUv3 host. LEARN MORE & HEAR: audiokitpro.com/retrokeys --- * LEGAL NOTICES Retro Keys is not affiliated with or endorsed by any keyboard or instrument manufacturer. All product names and images, trademarks and artist names are the property of their respective owners, which are in no way associated or affiliated with AudioKit Pro, LLC. Product names and images are used solely for the purpose of identifying the specific products related to sampling, sound design, and music making. Use of these names and images does not imply any cooperation or endorsement.
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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.
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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.
