How I Use Cthulhu as My Session Player in Music Production

When I first started producing, when it came to music theory and composition, I’d rely on session players to add chords, rhythms, and melodies, allowing me to focus on production. If I needed a specific progression or musical movement, I’d book a musician, have them play what I needed, and shape everything from there.

Over the years, I’ve learned a lot about music theory, allowing me to be more hands-on with composition. I’ve found modern tools that work as my virtual session players. These plugins give me the same kind of instant creativity and inspiration, allowing me to quickly build musical foundations without slowing down my workflow.

I’ve explored many MIDI tools, including Cthulhu, Scaler 2, Captain Chords, and EZ Keys—each offering something unique. While I create in many different ways, Cthulhu remains a leader for fast and effective melodic and rhythmic generation.

How I Use Cthulhu to Shape My Tracks

Step 1: Starting with Chord Progressions

When beginning a track, I usually start with a strong chord progression. In Logic, I load up a progression I like and place it on the same track as Cthulhu.

Phrygian chord progression in Logic Pro

Cthulhu on Channel Strip

Then, I engage Learn Mode, allowing Cthulhu to read the chords in real-time.

Cthulhu learn engaged

This means that whenever I place a note in Cthulhu’s grid, Cthulhu intelligently selects and plays from the chord I’ve fed it, allowing me to create natural and evolving movements instantly

Step 2: Using Cthulhu for Rhythmic Patterns & Arpeggiation

I have a folder of custom rhythm presets that I’ve built over the years. These rhythms allow me to quickly shape a groove without having to manually program each note in a DAW piano roll.

A selection from my rhythm folder

By default, Cthulhu loads with a 16th-note continuous arpeggio (the first arp setting in the top section of the grid). This is useful, but the real power of Cthulhu lies in the bottom section of the grid, where you’ll find eight numbered slots.

Cthulhu Grid

These numbers correspond to the notes within the chord—1 represents the first (lowest) note, 2 the next note up, and so on. If a chord has only five notes, slot 6 on the grid will cycle back to the bottom note of the chord, continuing the sequence from there.

Here’s how I use them:

🎵 Slot 1 → Plays the first note of the chord (great for basslines).

🎵 Slots 2-5 → These work well for creating mid-range melodies.

🎵 Slots 6-8 → These are perfect for top-line constants

Step 3: Crafting the Perfect Movement

One thing I love about Cthulhu’s rhythm sequencing is the way it allows me to shape movement in different ways.

✅ For contained, resolving melodies and basslines, I find that using 1 or 2 bar progressions work best.

✅ For longer, evolving phrases, I use anywhere between 8 to 32-bar progressions, which helps create a more drawn-out movement in the track.

I often start with the bass notes in Slot 1, then copy the bass channel/track and use Slots 2-5 for melodic variations. I do the same again with Slots 6-8, creating higher-register constants and melodies that sit above everything else.

This setup allows me to generate intricate, evolving musical phrases in seconds, without manually programming every note.

Cthulhu demonstration for basslines and melodies

Why I Still Use Cthulhu in 2025

Even though Cthulhu has been around for years, it still delivers incredible results. While modern tools like Scaler 2 and Captain Chords offer powerful composition features—and I’ve created great results with them—Cthulhu remains unmatched in its speed, rhythmic flexibility, and intuitive workflow.

Rather than just being an arpeggiator, I see Cthulhu as a tool that takes my chords and breathes rhythmic life into them. It allows me to quickly experiment, change directions, and refine ideas without breaking creative momentum.

Final Thoughts

When I need quick access to harmonically rich ideas, Cthulhu is my go-to. It helps me build grooves instantly and keeps my creative workflow fast and fluid.

With Cthulhu's other grid options—random, octaves, pitch, velocity etc —the possibilities are entirely down to preference. Every adjustment shapes how the sequence flows, giving you full control over your sound.

If you’re looking for a tool that can generate complex melodies, basslines, and chord movements quickly, Cthulhu is still one of the best out there.

Are you using Cthulhu in your workflow? What are your favourite chord/melody tools? Drop a comment below! 🚀🎶