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Review of RapidComposer music prototyping software (version 4.7) by Music Developments


The last time I did a review of RapidComposer was for version 3.4, back in 2018.

There’s been a huge number of changes since then – revamped rhythm and phrase generators,  a redesigned interface, improved resolution, more chords and progressions, improved midi, VST3 support and many more fixes and improvements.

In essence RapidComposer is a unique, non-destructive, phrase-based music prototyping software designed for composers, song-writers and musicians of all musical styles for both Windows and macOS.

It is available in two versions

  1. Light edition typically priced at $79 +VAT has Core functionality, VST/VST3 and soundfont support, standalone and VST versions (Windows and macOS), all updates until v5.99, thousands of reusable phrases and product support.  
  2. Full version typically priced at $199 +VAT includes all of the light edition features plus 3 Melody Generators, Idea Tool, MIDI Mutator, Melody Editor, Percussion Generator, articulations, phrase morphing.

Both versions are available direct from the MusicDevelopment website:

This review is for the full license of RapidComposer, version 4.7 released in June 2023.


The basic idea of RapidComposer is that you create your composition style and length, add chords, add basslines, add melodies and harmonies on as many tracks as you need.  You can load soundfonts or VSTs to hear your composition and then export as audio or midi files you can load into a DAW for further processing.  The VST that runs inside a DAW is a smaller version that communicates with the standalone version.  You can use RapidComposer to control separate VSTs or a multichannel VST such as Kontakt.

It has incredible depth and is a very powerful composing tool for any style of music.  It’s very flexible because it allows you to create your composition to any length and any format.  Although it comes with a number of chord progressions built-in, you are not limited to these and can add your own chords and furthermore there are many phrasing options too as well as options for piano and guitar chords.

There are also a huge number of scales and modes and a number of generators to create musical phrases which can be used as is or you can edit them to suit your needs. 

I would also point out that RapidComposer is not designed for mixing and mastering, it is designed as a compositional tool.

I found there is a learning curve getting to grips with the workflow but once I mastered this, the process of scoping out a song was pretty quick.  I’ve been happy using the standalone version and exporting to midi for import to Reaper DAW because I can then fine tune the VST instruments and effects that I’m using to mix the composition.  

What I really like about using version 4.7 is that it feels familiar to the previous version I used / reviewed so there is an instant familiarity but with an improved interface and many more composition tools, chord progressions and scales.

In Use

It’s worth spending time getting to grips with the interface and its functionality because the basics are pretty straightforward once you get the hang of the terminology and icons.  As with other music software, there are often several different ways of achieving the same outcomes.

Starting a new composition creates a 4 bar song with one track and a default I IV V I progression.  At this point, you have the basics of your song which you need to customise to your requirements.

Understanding terminology is a key part of using RapidComposer.  A composition is the entire song and comprises of one or more tracks which contain an instrument which in turn is controlled by phrases or phrase generators.  

A phrase is a sequence of notes or chords created and manipulated by one of the many rhythm and phrase generators.  Phrases can contain chord relative / scale relative notes or absolute notes but I find relative notes better to work with because I find it easier to think of a chords’ relative position in a scale and it also makes it easier transposing between keys.

The composition itself has a hierarchic structure with parts and lines.  This is incredibly flexible, you can change the name (i.e. intro; verse 1, line 1, line 2; chorus etc.) as well as duplicate, set bar length and colour code them.  As you add new parts and lines they inherit the properties of those above i.e. scale, tempo and signature but you can also override these values.

I must admit that some compositions of mine in the past have only used one part but I’ve found this is rather an unwieldy way to do things because there’s a lot of scrolling through the composition and editing is more challenging than it needs to be.  A bit of planning for the composition structure means that you can then easily duplicate and modify parts and lines which helps build your composition much more quickly and easily. 

You can now start adding notes to the composition and you do this using one of the phrase generators.  There are a lot of these covering chords, basslines, melodies, percussion, strings and random melodies and many others.  The power of RapidComposer comes in its ability to generate phrases which you can then edit, resize and add variations to.  

There are a couple of ways to do this – for example drag and drop or use keyboard shortcuts.  There are a number of options such as ‘join’ which creates chords that fill each bar and ‘lock’ and ‘magnet’ options which affect how phrases behave when transposed.

Changing chord progression is very easy.  You can see from the chord progression selection option there are a huge number of progressions available within RapidComposer.  I’ve selected one from the major scale and it’s a simple case of dragging and dropping onto your track as shown below.

You can then edit the chords in the progression and there are a number of ways to do this for example using the chord selector, circle of fifths chart or tonnetz – a 2d lattice showing harmonic relationships between chords.  You can also easily edit the chord length and each chord can have as long or short length as required.

At this point you can duplicate the line or part or add a completely new part.  For this example I’ve duplicated the part, changed the chords and chord lengths and changed the colour so I can distinguish between the two parts.

In order to build your song you would then add further tracks and populate them using the various generators.  For example, I’ve added a bassline and a melody line as shown below.

This is a fairly simple example but hopefully illustrates how quickly and easily you can create songs in RapidComposer.

To be honest, it feels like I’m barely scratching the surface because there are extensive customisation options available should you wish to use them.  For example, for phrases, you can apply variations such as add / extract notes, use double notes, offset notes, humanise, apply rhythms and many more.  This allows you to tweak individual phrases or the whole composition to add depth and variety to your compositions.

RapidComposer gives you a huge amount of control and tweakability for your composition which you can make as simple or complex as you like.  With such a huge number of chord progressions, scales, generators and customisation options I don’t think you would ever run out of inspiration. 

Another excellent feature available in the full version is the idea tool.  Essentially this lets you create a composition with a random or key-specific or rule-based Chord Progression and include any number of Phrases or Phrase generators which can be arranged in a fixed or random pattern.  It also provides optional rhythm patterns and phrase variations.

Idea Tool

This is a very simple 2 chord pattern.  I’ve used the idea tool to generate the master track and individual tracks, you can also use a melody track and RapidComposer will harmonise the melody track; set up the master track chords and then generate other tracks or you can generate a melody track based on the current master track. Then the new melody is harmonized on the master track and all other tracks are generated afterwards. 

There are different options for generating master chords – a random progression within a scale; choose a list of possible progressions and one will be randomly chosen from the list; A progression can be created by choosing a scale and chord progression rule; RapidComposer can select from specified progressions with absolute chords and find a suitable scale or you can select a random progression from absolute chords and find a suitable scale.

You also have options to arrange phrases in particular ways, add variations and you can regenerate individual tracks if required.  It is an incredibly powerful and easy to use tool, it’s a great addition to RapidComposer.


What I love about RapidComposer is that it is constantly evolving yet this is more of an evolution than a revolution.  The GUI will feel familiar if you’ve used previous versions with new tools available and a whole number of improvements and fixes that make it easier to use.  Even if you are new to RapidComposer, there is a learning curve but this is not that steep to get to grips with the basics and then you can start tweaking and customizing which are equally as easy to learn.

It has a very flexible structure to create compositions of any length and format.  There are a huge number of phrase generators that have extension options but you can also use random generation to get new ideas. It has an absolute ton of chord progressions that can provide inspiration and fresh ideas plus extensive chord options and scales.  The improvements have made it even more powerful, flexible and easier to use.

The flexibility allows you to create and export a composition within the standalone version, use the VST version directly within a DAW to control a number of virtual instruments or create a composition that you can export to midi files to import into a DAW separately for fine tuning instrument and effect settings. 

It is a complete compositional tool.  It is especially helpful if you struggle to create melodies, basslines, orchestral parts etc. because you can use the generators to create these specific parts.  That said, it is equally easy to create whole songs in pretty much any style with extensive customisation and tweaking options to get exactly the sound you want.

I’ve used RapidComposer to create the track embedded at the top of the post.  I’ve chosen the key of E minor and chosen a four chord progression starting with the Im chord.  I’ve then created the song using variations of this chord progression and used the idea tool to create various melodies, bassline and percussion parts.

I’ve then exported individual midi stems and imported into Reaper.  I’ve used a number of Spitfire Audio libraries and Eventide reverb and delay.  Interestingly, some tracks were better suited to different instruments than originally planned and some tracks layered much better with certain ones than others so part of arranging and mixing in Reaper was deciding which layers worked well together.

Incidentally, the song was a submission for the weekly Naviar Records Haiku Challenge, definitely worth checking out if you’re not already familiar.