# Key Finder MCP

> The Relative & Parallel Key Finder instantly maps out every structural relationship between musical keys. Give it any key, and it returns all its related partners—relative, parallel, homonymous, and those separated by a third-distance interval. It's an essential reference tool for composers needing instant analysis of Western music theory.

## Overview
- **Category:** education
- **Price:** Free
- **Tags:** music-theory, composition, key-signatures, modulation, musicians

## Description

Writing music often means knowing the rules first. This MCP connects your AI agent to complex Western music theory logic. Need to know every possible key related to C Major, or figure out exactly how many flats a specific key signature needs? This utility handles all that structural mapping for you. It's perfect for composers and students who need fast, reliable answers about harmonic relationships. Instead of flipping through thick textbooks or cross-referencing multiple charts, your AI client pulls the data directly. Vinkius hosts this MCP as part of a massive catalog, so once you connect your preferred agent, you gain instant access to all these musical tools. You just ask for the relationship between keys, and it provides a complete map.

## Tools

### find_key_relationships
Finds all structural partners for a key, including relative, parallel, antiparallel, homonymous, and third-distance keys.

### get_signature_details
Describes the technical composition of a given key by reporting its accidental count, type (sharps or flats), and mode.

### lookup_modulation_guide
Accesses a complete reference table detailing all known musical key signatures for modulation planning.

## Prompt Examples

**Prompt:** 
```
What is the relative and parallel key of G Major?
```

**Response:** 
```
The relative key of G Major is E Minor, and its parallel key is G Minor.
```

**Prompt:** 
```
How many sharps are in the key of D Major?
```

**Response:** 
```
D Major has 2 sharps (F# and C#).
```

**Prompt:** 
```
Show me all keys that share the same tonic as Eb Major.
```

**Response:** 
```
The homonymous keys for Eb Major are Eb Major and Eb Minor.
```

## Capabilities

### Map key relationships
It determines relative, parallel, antiparallel, homonymous, and third-distance partners for any given key.

### Detail key signatures
It provides a technical breakdown of any key's signature, detailing accidental count, type (sharps/flats), and mode.

### Reference modulation guides
It pulls up a complete reference table listing all known key signatures for planning modulations.

## Use Cases

### The Bridge Problem
A composer needs a key change for the bridge section but isn't sure which keys are harmonically related to the main verse. They ask their agent, and it uses `find_key_relationships` to provide several viable options (relative, parallel) that fit the existing harmonic palette.

### The Theory Exam Prep
A music student is studying key signatures for an exam. Instead of memorizing charts, they use `get_signature_details` to check how many accidentals a specific key has and whether it's in major or minor mode.

### The Arrangement Update
An arranger needs to map out the entire song structure for potential key changes. They use `lookup_modulation_guide` first to get an overview, then confirm specific transitions using the full scope of keys found by `find_key_relationships`.

### Identifying Tonal Centers
A sound designer wants to know all the tonal centers that share the same underlying accidentals as a given key. They use `get_signature_details` to verify the exact accidental count, helping them build cohesive soundscapes.

## Benefits

- Instantaneous Key Mapping: Using `find_key_relationships`, you stop guessing. You immediately see all the relative, parallel, and homonymous partners for any key, keeping your compositions harmonically tight.
- Technical Clarity on Signatures: Never doubt a key's composition again. `get_signature_details` instantly tells you if a key has sharps or flats, how many, and what mode it uses.
- Modulation Planning Support: Need to move from one section of music to another? The `lookup_modulation_guide` gives you a complete reference chart for reliable key changes.
- Saves Research Time: Instead of cross-referencing multiple charts or flipping through textbooks, your agent pulls this complex theory data in seconds.
- Structured Output: All results are delivered cleanly. You don't get raw data dumps; you get actionable lists and detailed reports for immediate use.

## How It Works

The bottom line is you get an immediate, expert-level analysis of complex key relationships without doing the math yourself.

1. You ask your AI client to find the structural relationships or details of a specific musical key.
2. The MCP uses its internal logic to calculate and retrieve all necessary harmonic data based on standard music theory rules.
3. Your agent receives a clean, structured list containing relative keys, signature counts, or full modulation reference tables.

## Frequently Asked Questions

**How do I use find_key_relationships to find all related keys?**
You simply ask your agent for the relationships of a specific key. For example: 'What are the find_key_relationships for C Major?'. The tool returns every structurally linked partner in one list.

**Does get_signature_details only count sharps?**
No, it reports on both sharps and flats. You can ask it to check the signature details of any key, and it will give you the total accidental count, type (sharps/flats), and mode.

**What is lookup_modulation_guide used for?**
It provides a full reference chart showing all known keys. This guide is crucial when planning large-scale modulations across an entire piece of music.

**Can I use find_key_relationships to compare multiple keys?**
Yes, you can ask the agent to compare two or more keys using this tool. It will then list all the structural relationships that exist between them.

**Is this useful for simple chord theory?**
This MCP focuses on deep harmonic structure and key relationships, not simple chords. Use it when you need to know *why* certain keys are related, not just what chords they contain.