Table of Contents

Interface IKeyDetector<T>

Namespace
AiDotNet.Interfaces
Assembly
AiDotNet.dll

Interface for musical key detection models that identify the key and mode of music.

public interface IKeyDetector<T>

Type Parameters

T

The numeric type used for calculations.

Remarks

Key detection identifies the musical key (e.g., C major, A minor) of a piece of music. The key defines the central note (tonic) and scale (major/minor) that the music is based on.

For Beginners: The musical key is like the "home base" of a song.

What is a key?

  • Every song has a central note that feels like "home"
  • The key tells you which note that is and whether it's major (happy) or minor (sad)
  • "C major" means C is home and it sounds happy
  • "A minor" means A is home and it sounds sad/dark

How key detection works:

  1. Audio is analyzed to find which notes are used most
  2. This is compared to key profiles (templates of note usage)
  3. The best-matching key is selected

Why it matters:

  • DJ mixing (match keys for smooth transitions)
  • Music recommendation (similar keys = similar feel)
  • Music production (know what key to write melodies in)
  • Transposition (shifting a song to a different key)

Related concepts:

  • Relative keys: Am is the relative minor of C major (same notes)
  • Parallel keys: C major and C minor (same root, different mode)

Properties

SampleRate

Gets the expected sample rate for input audio.

int SampleRate { get; }

Property Value

int

SupportedKeys

Gets the list of keys this model can detect.

IReadOnlyList<string> SupportedKeys { get; }

Property Value

IReadOnlyList<string>

Remarks

Typically 24 keys: 12 major + 12 minor.

Methods

Detect(Tensor<T>)

Detects the musical key of audio.

KeyDetectionResult<T> Detect(Tensor<T> audio)

Parameters

audio Tensor<T>

Audio waveform tensor [samples] or [channels, samples].

Returns

KeyDetectionResult<T>

Key detection result.

Remarks

For Beginners: This is the main method for finding the key. - Pass in audio of a song - Get back the key (e.g., "C major" or "A minor")

DetectAsync(Tensor<T>, CancellationToken)

Detects the musical key asynchronously.

Task<KeyDetectionResult<T>> DetectAsync(Tensor<T> audio, CancellationToken cancellationToken = default)

Parameters

audio Tensor<T>

Audio waveform tensor.

cancellationToken CancellationToken

Cancellation token for async operation.

Returns

Task<KeyDetectionResult<T>>

Key detection result.

GetCamelotNotation(string)

Gets the Camelot wheel notation for a key.

string GetCamelotNotation(string key)

Parameters

key string

The key to convert (e.g., "C major").

Returns

string

Camelot notation (e.g., "8B").

Remarks

For Beginners: The Camelot wheel is a DJ tool that shows which keys mix well together. Adjacent numbers on the wheel = compatible keys.

GetCompatibleKeys(string)

Finds compatible keys for mixing.

IReadOnlyList<string> GetCompatibleKeys(string key)

Parameters

key string

The reference key.

Returns

IReadOnlyList<string>

List of compatible keys for harmonic mixing.

GetKeyProbabilities(Tensor<T>)

Gets key probabilities for all possible keys.

IReadOnlyDictionary<string, T> GetKeyProbabilities(Tensor<T> audio)

Parameters

audio Tensor<T>

Audio waveform tensor.

Returns

IReadOnlyDictionary<string, T>

Dictionary mapping key names to probability scores.

Remarks

For Beginners: Some songs are ambiguous - they might sound like they're in C major or A minor (these share the same notes). This method shows the probability for each possible key.

GetRelativeKey(string)

Gets the relative major/minor key.

string GetRelativeKey(string key)

Parameters

key string

The key to find the relative for.

Returns

string

The relative key.

TrackKeyChanges(Tensor<T>, double)

Tracks key changes over time within a piece.

KeyTrackingResult<T> TrackKeyChanges(Tensor<T> audio, double segmentDuration = 5)

Parameters

audio Tensor<T>

Audio waveform tensor.

segmentDuration double

Duration of each analysis segment in seconds.

Returns

KeyTrackingResult<T>

Key tracking result with key over time.

Remarks

For Beginners: Some songs change key during the song (called modulation). This tracks those changes over time.

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