String Finder
Start here if you need to replace one string. OpenHarp helps you measure, identify, and request a replacement safely when you do not have the original chart.
Start Here
One Broken String
Use String Finder. Confirm the note, measure vibrating length, and use the supplier-ready request text.
No Chart For Your Harp
Use Chart Builder after measuring lengths. Treat wound bass strings as supplier-matched.
Want Better Accuracy
Use Harp Profiler to estimate your harp's actual tension, then lock it into String Finder.
About OpenHarp
OpenHarp is an open-source measurement and physics tool for identifying replacement harp strings when charts are missing, incomplete, or hard to access.
Why It Exists
String charts are often difficult to access. OpenHarp helps players measure what they have and make an informed replacement request.
Safest Path
The safest option is still an original maker or trusted supplier chart for your exact harp model. Use that first when available.
Important Risks
- Wrong string material or tension can affect tone and playability.
- Wrong bass/wound strings can stress the harp or perform poorly.
- When in doubt, order by note + vibrating length from a harp supplier.
Confirm the note
Measure vibrating length
Get a replacement recommendation
Advanced options (material, tension, comparison tools)
Advanced tool: back-calculate tension from known gauge
Chart Library
Browse OpenHarp chart data in our own JSON format. Each entry shows where the data came from and whether it is a public official chart transcription or a recreated/community-style chart.
What you are looking at
Official / Public Chart
Transcribed factual data from a publicly available maker or supplier chart (for example, printable PDF charts). OpenHarp stores facts, not the source PDF.
Recreated / Estimated
Built from measurements, physics, or partial evidence when no chart is available. These are useful, but need extra caution and verification.
Verification Status
Charts are labeled needs review or verified so you can judge confidence before ordering.
Available OpenHarp Charts
Select a chart to view the string table and provenance details.
Chart Builder
Build a working chart when an official chart is missing. The more measured vibrating lengths you enter, the more reliable the result.
Step 1 â€" Define your harp
About & Method
What OpenHarp Is (and Is Not)
What It Is
A measurement and physics tool for identifying and documenting harp strings when charts are missing, incomplete, or hard to access.
What It Is Not
It is not a replacement for an authoritative maker/supplier chart for your exact harp model when one is available.
Why This Matters
The wrong string can affect tone, response, and tension. OpenHarp is designed to help you make safer, better-documented choices.
The Mersenne-Taylor Law
Every vibrating string obeys the same fundamental physics:
Where:
- f â€" fundamental frequency (Hz) â€" fixed by musical note
- L â€" vibrating string length (m) â€" measurable with a ruler
- T â€" tension (N) â€" target design parameter
- μ â€" linear mass density (kg/m) = Ï Ã— Ï€ × (d/2)²
- Ï â€" material density (kg/m³) â€" known for each material
- d â€" string diameter â€" what we solve for
Solving for d:
The underlying physics is well-established and openly documented. For best results, combine these calculations with maker-specific guidance for your instrument.
How to Measure Your Harp
You need one measurement per string: the vibrating length â€" from bridge pin to the lever blade (or nut on a stringed instrument without levers).
- Start from string #1 (highest/shortest)
- Hold a ruler parallel to the string
- Measure from bridge pin to the lever blade contact point
- Record in millimeters
- Repeat down to the lowest string
Tip: C strings are red, F strings are dark/black. Use a tuner to confirm notes.
Material Reference
| Material | Density (kg/m³) | Common use | Notes |
|---|---|---|---|
| Nylon monofilament | 1,140 | Folk / lever harps, treble + mid | Durable, affordable, widely available |
| Natural gut | 1,300 | Pedal harps throughout; some lever | Warm tone; humidity-sensitive |
| Fluorocarbon (KF) | 1,780 | Alternative to gut; all harp types | Stable in humidity; similar to gut in feel |
| Steel wire | 7,800 | Wire-strung / Celtic harps | Bright, metallic tone; high tension |
| Bronze / Brass wire | 8,600 | Wire-strung harps | Warmer than steel |
| Wound â€" copper on nylon | ~2,200 | Bass on folk harps (~G3 and below) | Custom-made; simple gauge formula doesn't apply |
| Wound â€" silver on gut | ~2,800 | Bass on pedal harps (~E3 and below) | Custom-made; contact a specialist supplier |
Common Practice (What Suppliers Expect)
OpenHarp follows the same practical workflow used by harp string suppliers and replacement guides: start with the harp model and maker chart when available, and use note + vibrating length when a chart is missing.
- Use the original chart first (maker or supplier chart for your harp model) whenever possible.
- Measure vibrating length (speaking length) and confirm the note before calculating.
- Match material family by register (nylon/gut/fluorocarbon/wire), not just diameter.
- Treat wound bass strings as custom parts: order by note + length from a harp supplier, not by monofilament gauge math alone.
- Snap to stocked gauges and verify tension so replacements map to what suppliers actually sell.
- Replace like-for-like if the harp is stable and sounds right; use profiling only when you are intentionally reverse-engineering a missing chart.
OpenHarp is a measurement + physics fallback for missing charts, not a replacement for an authoritative maker chart when one exists.
Public String Chart Links (External)
Before building your own set, check whether a public chart already exists for your harp. OpenHarp links these resources but does not mirror third-party PDFs without permission.
- Sylvia Woods Harp Center Printable String Lists - public chart hub with many maker/model links.
- Harp.com String Information - model guidance and replacement resources.
- Markwood Heavenly Strings - chart lookup and custom matching support.
If you find a chart, use it. If you only have partial information, OpenHarp can still help you measure, verify, and communicate the right specs.
Contribute
Help build an open, reviewable string chart commons. Measured lengths, transcribed public chart facts, and verified replacement outcomes are all useful.
The most valuable thing you can do
Measure your harp's string lengths and submit them. Your data helps every other owner of the same model â€" forever.
- Measure your strings (see About & Method → How to Measure Your Harp)
- Use the String Finder to verify the gauges make sense
- Email your measurements to us or submit them through our GitHub page
For technical contributors: Charts are stored as JSON files. See data/harps/lever/rees-harpsicle-26.json for an example format. Unknown fields go in as null. Partial data is always welcome.
String Suppliers and Charts
Start with your harp maker or a harp-focused supplier before substituting by guess. These are useful places to order strings, find charts, or verify a set.
- Markwood Heavenly Strings â€" large chart catalog and custom stringing analysis.
- Harp.com (Vanderbilt Music) â€" harp string selector and replacement resources.
- Vanderbilt Music Company â€" harp strings and gauges (including pedal/lever options).
- Bow Brand â€" major harp string manufacturer (gut, bass wire, etc.).
- Musicmakers â€" lever harp replacement strings and buying guidance.
- Sylvia Woods Harp Center â€" replacement strings, sets, and harp supplies.
If a supplier asks for a custom replacement, send the note, vibrating length, and material (plus your harp make/model if known).
Harp Profiler
Use this when you want better-than-default accuracy. Measure a few existing strings with a caliper, and OpenHarp estimates your harp's working tension so Finder/Builder match your instrument more closely.