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Chromatic HarpTabs

A focused tool for chromatic harmonica players to collect, read, and practice tabs with clear notation and mic assisted feedback during play.

Team Abiodun Adefusi & Joshua Tjhie
Repository Source code on GitHub

App Concept

Chromatic HarpTabs is a focused application for collecting, viewing, and practicing chromatic harmonica tabs. It provides a structured tab library with consistent notation for blow, draw, and slide use, and a practice mode designed for active playing. In addition to reading tabs, users can preview notes directly in the app using a virtual harmonica, allowing them to hear how passages should sound before playing them on a real instrument. The app emphasizes clarity, quick access, and practice oriented interaction rather than passive browsing.

Target User

  • Beginners learning chromatic harmonica who are not yet comfortable reading standard music notation.
  • Players transitioning from diatonic harmonica who are familiar with tab based notation.
  • Hobbyists who want quick reference material and practice support for simple tunes.

Use Case

Use Case – Tab Library & Music Practice

The app supports individual music practice by helping users organize and actively work with their learning material. Users can store their own chromatic harmonica tabs, read them in a consistent format, preview notes through a virtual harmonica, and practice along using a dedicated practice view. Optional microphone based feedback can support awareness during practice without replacing traditional learning methods.

User Flow

Hi‑Fi Prototype

Hi-fi prototype library screen
Library
Hi-fi prototype tab detail screen
Tab Detail
Hi-fi prototype tab editor screen
Tab Editor
Hi-fi prototype practice mode screen
Practice Mode

App Screenshots

A quick look at the core flows: library browsing, tab reading, the tab editor and practice mode.

Library screen
Library
Tab screen
Tab Detail
Tab editor screen
Tab Editor
Practice mode screen
Practice Mode

Difference Between Hi-Fi Concept and Final UI

While the high-fidelity concept provided a clear visual and functional direction at the start of the project, the final implemented UI differs in several aspects. As development progressed, time limitations, and feedback from testing required us to simplify and adapt certain design elements. Some interactions and layouts were adjusted to improve usability, performance, and stability, resulting in a more practical and focused interface. These changes reflect an intentional shift from a visually ideal concept to a solution that better supports real use within the project scope.

SQLite Database ERD

Room schema for the app database (single-table design).

Final Reflections

Abiodun Adefusi

Working on Chromatic HarpTabs was a very rewarding experience for me, as it pushed me into an area I had not explored before: sound, frequency, and audio interaction within a mobile application. Prior to this project, I had not worked on any app involving audio input, so it required substantial research and learning beyond my usual comfort zone.

Through this process, I gained practical insight into how sound is captured and processed on Android, how frequency maps to musical notes, and how audio feedback can be integrated to support learning and practice. Features such as the microphone-based practice mode, sound previews, and the interaction between UI and audio logic helped me understand the complexity of building responsive, real-time audio features on mobile devices.

One of the key challenges was identifying and working with an appropriate target audience. Chromatic harmonica players represent a very niche user group, and within the limited timeframe, access to a large number of representative users was not feasible. Usability testing was therefore conducted with the available testers, resulting in a smaller test group and requiring careful task design to still obtain meaningful insights.

From a development perspective, the project involved continuous iteration and prioritization. We focused on stabilizing core features before extending functionality, repeatedly refining UI components to maintain reliability as the app grew. This highlighted the importance of clear scope definition and iterative improvement, particularly in a small two-person team.

Overall, I am glad of what we achieved with the Chromatic HarpTabs. The project expanded my technical skill set especially in audio handling and user experience design, while strengthening my ability to adapt to unfamiliar domains, work within testing constraints, and collaborate effectively under time pressure.

Joshua Tjhie

Chromatic HarpTabs has been a very interesting project to work on for me, particularly as it is for a very specific and niche use case, one made specifically for my personal use as a chromatic harmonica player, and of course for others that also play (though I personally know of no other as of yet).

As we wanted to get it done within a week or two, we chose to have a very good jumping off point, that is my Mobile Coding project, which essentially is the same app but with very basic CRUD functionality and without any audio input & output features (microphone practice mode, virtual harmonica, sound previews, etc.) and polish.

Challenges that came from this project were mostly about figuring out how to polish certain UI features, their stability, constant testing and feedback taking, practice/mic reliability, scaffolding the project, having to refactor every time something grew too large, system redesigns (JSON), prioritizing certain features over others, Gradle and Room breaking for a reason I still have no clue of, and more. Testing also became harder the more polished the app is as most would not be able to find the usability issues as easily.

There are many ways in which the app can still be improved and built upon. We could implement a JSON export/import function for the tabs relatively easily as they are already formatted in such a way for example. Another improvement can be a shared online database for sharing tabs, and perhaps a tempo visualization for song flow (though that goes beyond the scope of tabs and then perhaps redundant to proper musical notation).

I am very proud of this project, and have made practical use of it myself for practicing with the chromatic harmonica.

Mean SUS
95.42
Perceived usability (n = 6)
Critical Issues
1
Severity 4
Participants
6
Moderated user tests
Top Support Task
T4
Create a new tab

1. Usability Test Plan

This evaluation assesses the effectiveness, learnability, and user satisfaction of the ChromaticHarp Tab App

Goals

  • Verify users can complete core workflows successfully.
  • Identify learnability barriers (especially for novices).
  • Measure perceived usability using SUS.
  • Capture issues using Nielsen’s heuristics + severity ratings.

Approach

  1. Heuristic evaluation of the initial prototype.
  2. Moderated user test with task-based protocol + SUS.

2. Heuristic Evaluation (Initial Prototype)

We used Nielsen’s 10 usability heuristics to identify potential risks prior to user testing. Key areas of concern included error prevention, visibility of system status, and help/documentation for first-time users.

Note: This heuristic review reflects the initial prototype (before incorporating user-test feedback).

Heuristic Evaluation Table (Initial Prototype)

Severity scale: 0 = No problem · 1 = Cosmetic · 2 = Minor · 3 = Major · 4 = Critical

S/N Screen / Feature Nielsen Heuristic Agreed Severity Suggested Improvement
1LibraryVisibility of system status2Indicate clearly when search, filters, or sorting are active (visual highlights or status indicators).
2LibraryRecognition rather than recall2Make filtering and sorting options more visible so users do not have to remember where options are located.
3LibraryConsistency and standards2Align search bar behaviour and icon usage with common Android list/search patterns.
4Tab DetailUser control and freedom3Provide clearer navigation and safe exit paths, especially for destructive actions such as delete.
5Tab DetailError prevention3Add safeguards to prevent accidental deletion or unintended actions.
6Tab DetailMatch between system and real world2Improve terminology and iconography to better reflect how users naturally think about tabs and songs.
7EditorError prevention3Prevent accidental loss of work by ensuring users are warned before exiting with unsaved changes.
8EditorUser control and freedom2Allow users to easily cancel or undo actions during editing without confusion or fear of losing progress.
9EditorRecognition rather than recall3Reduce the need to remember notation rules by providing inline hints or visible guidance within the editor.
10PracticeVisibility of system status3Make it clearer which part of the tab is currently being practiced and how progress is structured.
11PracticeFlexibility and efficiency of use2Support efficient navigation for experienced users (e.g., quicker movement between lines).
12PracticeAesthetic and minimalist design1Minor visual refinements to keep focus on the active practice content without unnecessary distraction.
13GlobalConsistency and standards2Ensure consistent visual language, icon behavior, and navigation patterns across all screens.
14GlobalHelp and documentation3Provide basic in-app guidance or onboarding to explain core concepts and workflows.
15GlobalHelp users recognize & recover from errors2Use clearer feedback messages when something goes wrong and indicate how the user can recover.

3. Hypotheses / Testable Questions

  • H1: Users can complete all main tasks without failure.
  • H2: Users without harmonica experience can still use the app effectively.
  • H3: The app achieves a high SUS score (≥ 80).
  • H4: Creation/editing tasks require more support than browsing/practice tasks.

4. Planned Data to Collect

Quantitative

  • Task outcomes per task: S (Success), P (Partial with hint), F (Fail)
  • SUS scores (0–100)
  • Participant demographics (age, harmonica experience, tab-app experience)
  • Counts of partial completions per task

Qualitative

  • Moderator observations during task execution
  • Oral feedback and notable quotes
  • Usability issues mapped to Nielsen heuristics
  • Issue severity ratings (1–4)

5. Methods Used (User Test)

Participants

n = 6, majority novice harmonica users.

Environment

  • Android smartphone + Chromatic App prototype
  • Think-aloud protocol encouraged
  • Sessions recorded for observation notes

Measures

  • Task outcome per task (S, P, F)
  • System Usability Scale (SUS)
  • Heuristic issue mapping + severity (1–4)

Protocol

  1. Briefing: explain goals, consent, and expectations.
  2. Warm‑up: short demo of app structure (no task hints).
  3. Task run: six scenario‑based tasks with think‑aloud.
  4. Post‑test: SUS questionnaire + open feedback.

Tasks

Task ID Scenario Success Criteria
T1 “Find a tab titled Amazing Grace and open it.” User locates the tab using search or scrolling.
T2 “Show only Medium difficulty tabs and sort them by newest.” User successfully applies and removes filters and sorting.
T3 “Mark any tab as a favourite and show only your favourite tabs.” User understands favorite functionality.
T4 “Create a new tab with a title, key, difficulty, tags, and at least two lines of notes. Save it.” User completes creation without external help.
T5 “Edit the tab you created, then try to leave without saving.” User understands discard/save dialog.
T6 “Start practice mode and move between different lines.” User navigates lines and understands practice flow.
Materials: SUS questionnaire (Google Forms), task observation sheet, and Python (Google Colab) for analysis and visualizations.

6. Results Overview

Mean SUS
95.42
Best imaginable usability range
SUS Range
87.5–100
n = 6
Critical Issues
1
Severity 4
Highest Support Task
T4
Create a New Tab

Highlights from the evaluation are summarized above; detailed charts are available in the visualizations section.

7. Data Visualizations

7.1 Demographics

Figure 1: Participant demographics (age group, harmonica experience, app experience).

7.2 SUS Results

Individual SUS scores: 95.0, 97.5, 95.0, 97.5, 100.0, 87.5. The mean SUS score (95.42) indicates excellent perceived usability.

Figure 2: SUS scores per participant with mean line (n = 6).
Figure 2b: SUS score distribution (boxplot).

7.3 Task Outcomes

Task Success Partial (Hint) Fail
T1600
T2510
T3600
T4150
T5510
T6600
Figure 3: Task outcomes derived from task ratings (5 = success, 4 = partial, ≤3 = fail).
Figure 3b: Task rating distribution per task (boxplot).

7.4 Issue Severity Distribution

Note: Severity data is not present in the current dataset, so this chart has been removed.

8. Most Relevant Feedback / Comments

“Add a popup prompt before deleting a tab just to confirm.”
“In the editing screen, add an info popup for notation editing to explain how it works.”
“Enter should also enter the tag.”
“The search bar is weird behaviorally.”
“Pressing cancel doesn’t bring up the popup like back.”
“Clear all filters button would help.”
“Show line number out of how many lines in practice mode.”
“Play the note on the editor screen.”
“The library icon looks like a button.”

9. Updates Made Based on Feedback

  • Delete confirmation dialog (and optional undo snackbar).
  • Info popup / tooltip for notation editing.
  • Enter/Done commits tags in the editor.
  • Improve search UX (clear state, consistent cancel behavior).
  • Add “Clear all filters” action in Library.
  • Add “Line X of Y” progress indicator in Practice.
  • Add note playback feedback in Editor.
  • Refine library icon styling to reduce false affordance.

10. Summary

The usability evaluation indicates excellent user satisfaction (Mean SUS = 95.42) and strong task performance (no failures). Most usability improvements are centered on learnability and feedback, especially for creation/editing workflows (T4). Implementing the proposed changes is expected to improve first-time user confidence and reduce reliance on hints.