App Overview

SoundFonts icon

SoundFonts

Brad Howes · Entertainment

This is a straightforward yet powerful app that acts as a polyphonic audio synthesizer with a virtually unlimited collection of sounds

$7.99 · In-app purchases

PRICE
$7.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
4.4
140 ratings · Top 30%

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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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.

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.

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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Good fit for mobile-first iOS and Android prototypes with managed app scaffolding.

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Rork plan preview for SoundFonts: map the core Entertainment 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

Offer more sound processing features and effects

Assumption to check: Limited sound customization options

Validate with people who use this workflow before building.

Hypothesis 2

Simplify subscription explanations and provide clear benefits

Assumption to check: In-app purchase confusion

Validate with people who use this workflow before building.

Hypothesis 3

Ensure smooth audio playback with adaptive buffering

Assumption to check: Occasional playback issues

Validate with people who use this workflow before building.

Hypothesis 4

Introduce user profiles, sharing, and commenting on sounds

Assumption to check: Lack of community features

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

This is a straightforward yet powerful app that acts as a polyphonic audio synthesizer with a virtually unlimited collection of sounds. Under the hood, It uses an AVAudioUnitSampler to generate the audio output when you touch one or more keys. The sounds that are available come from soundfont (SF2) files, such as those available online for free (and of variable quality).  The app also exists as an AUv3 plug-in (included) so you can use it in your favorite music generation application such as GarageBand, Logic, or AUM. It also includes two AUv3 effects units – reverb and delay - which you can use separately as well.. The app supports MIDI input -- just connect a MIDI keyboard/controller to your iOS device and you should be good to go! There is also support for MIDI over Bluetooth. You can also control some app settings using MIDI controls, including the active favorite preset and the audio effects. To use, simply select a SoundFont name in the left list, then a patch name on the right and start playing. Some additional hints to get going: • Add a SoundFont (SF2) file that you have downloaded onto your iCloud Drive. Press the "+" button and then locate the file to add. You can always change the display name of the SoundFont by swiping right. And you can remove a SoundFont that you no longer want by swiping left on its name. • Bring up reverb and delay effects by touching the wavy "signal" button. • Swipe right on a patch name to make it a favorite. Favorited patches have a star next to their name. You can edit the name of the favorite by again swiping right and selecting the edit action. You can remove a favorite by swiping left and selecting the remove action. • Touch the labels at either end of the black bar to change the range of the keyboard. You can go as low as "C0" and as high as "C9". You can also change the range by swiping left/right on the black bar. Note that this ability does not exist in the AUv3 extension -- use the native application keyboard controls to achieve the same results. You can also toggle the keyboard sliding feature by touching the small arrow between the note labels. • Switch between the soundfont patches listing and the favorites view by double-tapping on the patch name in the black bar above the keyboard. You can also swipe left/right with two fingers in the patches and favorites views to switch to the other view. • In the view of favorites, you can edit a favorite button by double-tapping on it. You can rearrange the favorite buttons with a tap-and-hold gesture. Finally, you can check out the source code! Go to the Support URL to find out more.

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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.

SUGGESTED BUILD STACK
React Native
Expo
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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.