HoRNet SongKey MK4

SongKey MK4 4.0.3 is available, this update is free for owners of the plugin and includes:

  • Fixed macOS app not requesting permission to use audio input
  • Added audio passthrough to stand alone app in mac and windows
  • Slightly reduced CPU load

Realtime chord, tempo and key finder plugin

HoRNet SongKey MK4 is the fourth version of our key recognition tool, but it doesn’t do simple key recognition, it’s also capable of detecting the chord being played and the song tempo. We thought it was a good idea to also add MIDI input (to be able to detect chords and key of midi tracks) and MIDI output for the recognised chords so you can record them and edit the track for your own needs, also SongKey MK4 provides new standalone version that is able to generate midi clock to keep all your other M;IDI gear in sync with a live audio input. 

Of course this new SongKey provides better accuracy in every aspect: key recognition is faster and more precise, chords are detected more precisely and tempo is more accurate.

We have put great attention improving the “chromagram” a level representation of the intensity of each note playing in the song taking into consideration a wider range of octaves and filtering out some slight out of tune sounds. The data extracted from the audio is used to feed a simple artificial intelligence unit that is used to detect each chord, and SongKey MK4’s chord detection extends to sevenths, fifths and suspended chords.

The new key detection engine builds on the chromagram and expands it with another artificial intelligence unit based around a statistical chord progression model that analysing the chord sequence is able to understand the key of the song, this has the great advantage that the key recognition is always realtime so you can change song without the need to reset the plugin, or if the song changes key in some part of it, the plugin will simply be able to detect the new chord sequence and follow the key change, all of this working just on your DAW, with no need for an internet connection.

The two chromagrams (the one used for chord recognition and the one for key recognition) are shown on the GUI so that you can know which notes are playing and which ones you can use for your track, also we added a handy keyboard display that allows you to see which keys are being played. This is extremely useful if you use SongKey MK4 for acapellas or other samples, with a quick look you can know the key of your samples and which notes to use in your tracks to complement those samples.

Finally we have an accelerated and resizable vector GUI that looks good on any display, even if you double its size.

The new SongKey MK4 also comes as a standalone App for macOS and Windows, this allows you to feed it with any sound from your other apps and see SongKey’s analysis in real-time, you can also use a live recording or a band playing live as its input, since it generates MIDI clock from the detected tempo, it can drive another DAW or sequencer and keep it in time with the live sound.

SongKey is very useful in those situation in which you don’t have an instrument at hand to find out the key of a song you are working on or if you are a DJ and want to make a mash up but you don’t know in which key a song is written. The chord detection feature gives you insights on the chord progression of the song so that you can better design your bass lines and pads.


We decided to not provide a demo for SongKey MK4 because we don’t want to to cripple our product too much and limiting the capability of this plugin for a demo would mean to provide a bad testing experience.

For this reason we offer an instantaneous full refund within 15 days of your purchase if you buy SongKey MK4 and you don’t like it


  • Artificial Intelligence driven key identification that follow key changes
  • Realtime audio and MIDI chord detection
  • Confidence display for each found key
  • Key and Chord chromagram that shows each note level
  • Key and Chord piano roll view to see which notes are active
  • Sample mode for short sounds analysis
  • Realtime tempo detection
  • MIDI output of detected chords
  • Stand alone App for both Mac and Windows
  • MIDI clock output (in the stand alone App)
  • Sharp and Flat notation
  • Resizable vector GUI
  • Hardware accelerated GUI
  • Apple Silicon native support (except for AAX)
  • macOS (10.11 and later) and Windows (7 and later, OpenGL 2.1 required) support.
  • 64-bit only plugins for macOS and Windows.
  • Audio Units, VST, VST3 and AAX format.

Copy protection

The HoRNet SongKey MK4 has no copy protection, we don’t believe in copy protection, they are always cracked and they are annoying for the users, we all know you are not going to give away the plugin on the internet…

So simply download the plugin and enjoy your recordings!

Featured videos

19 thoughts on “HoRNet SongKey MK4

Troy says:

This is brilliant. Thank you!

Richard Dickson says:

Saverio, thanks! I just got this plugin. I can see how it could be helpful.

I watched the video on the sales page. However, how does the MIDI output work? I didn't see it reviewed in the video.

Andrew Webb says:

Not great. Wanted this for BPM detection. Even with an electronic pop drum generator, SongKey was several BPM off the actual tempo and it takes too long to register a change in tempo, if it detects the change at all. Has potential but not reliable.

David says:

I admit I use it a lot, for samples, tracks and root notes. The design is great, minimalist and overall clean. However, the accuracy decreases with the number of notes and, for example, chord-heavy EDM tracks are usually inaccurate by a semitone.

Jay Lane says:

This is decent for simple chords but seems to get confused when playing 5 or 6 note chords. Accuracy definitely dips when dealing with more complex stuff, hence the rating.

Colin Mansfield says:

Any idea when the AAX version will be ready for Pro Tools 2023 on Apple Silicon? Without it, my harmonies sometimes sound like a tone deaf Balkans choir… (Just kidding, but it IS such a useful plugin.)

Takeshi Kumagai says:

I think it would be useful to have a MIDI detection priority button and an audio detection priority button on the MK4.

Samuel says:

Very useful plugin, I really like the standalone app

Amazinbeats says:

Come to iOS Auv3 please

Gregory Timmons says:

Exactly what I need and no more.

I don't need more instruments, I don't need a ton of junk in my plugins. I just need to do one thing and one thing right. I'm very happy that Hornet Plugins has created this piece of software!

Franzzyyzz says:

El plugin es inestable y genera saturación de CPU en Ableton Live Standar 11.1.6.
Me estaba volviendo loco hasta que descubrí que este pequeño estaba usando el 100% de CPU. W10, I9 11900k, 32gb RAM DDR4, Disco Samsung nmve 1tb y pc a estrenar casi. Utizaba el 3 y no me pasaba nada de esto. Ya avisareis cuando lo solucionéis. Son buenos productos y me gusta la compañía.

Emmanuel Bégué says:

Tempo detection doesn't seem to work properly. For example for "Dirty Mind" (PandaBoyz) it says 123 bpm when the actual bpm is 126. That song has a strong kick & bass for the first 8 bars that should be easy enough to detect.

Nice plugin though… but a more reliable bpm detection would be nice.

Colonyrecords says:

I just bought but Im getting audio glitches in NI Maschine with this plugin, needs optimization. I tried both AU and VST same thing..

Jeff Malmud says:

I am a full time Mix Engineer. I didn't expect to, but I use Songkey MK4 regularly, and has been part of my Pre-Mix Template. since MK3, to verify my findings, It does what they say they'll do. Their free upgrades is an indicator to me of how much a company cares about their customers, as opposed to companies like the $29 special price company that nickel-dimes you at every turn. .

DJFLX says:

Thank you for the demo Saverio:) Fantastic plugin! I am not a musician but a producer and songwriter and this would really speed up the process of finding chords as base to be inspired from for an arrangement. I should definitely try it out.


Saverio Vigni says:

We updated drastically the detection engine with SongKey MK3, this update is an evolutive update keeping the same detection engine but improving the crhromagram generation. IF you want to know more just drop me a line

Saverio Vigni says:

could you please let us have the tracks that misbehave?

Saverio Vigni says:

Hi we'll shot a video soon demonstrating how the plugin works!

Jeff Mayer says:

Very useful plugin! I use it to quick balance all my imported track.

Question… is the MK4 update free to MK3 owners?

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