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Arpeggiator Plugin by CodeFN42
RandARP by CodeFN42 is a Virtual Instrument Audio Plugin for Windows. It functions as a VST Plugin.
System Requirements
Windows XP/Vista/7/8/10
Copy Protection
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RandARP is a VST plugin arpeggiator with many randomization features, allowing incoming notes or chords to be manipulated in various rhythmic ways. All standard arpeggiator parameters like number of octaves, note length and note order are included, but the plugin also offers complete randomization of the velocity, gate, shift and swing parameters.

In addition, you can specify a note probability and randomize the note order, the octave order, and the number of octaves. All the randomization features allows you to create more interesting and unpredictable arpeggiated sequences.

Freeware for Windows, both 32 and 64-bit.

Latest User Reviews

Average user rating of 5.00 from 3 reviews

Reviewed By elviecho
November 9th, 2021

A great plugin, like all the CodeFN42 stuff!
Set note order, octave order and swing to random and... pow, you are Roy Ayers. :-).

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Reviewed By groumpf
October 4th, 2021

I was searching a plugin that could replace the JS MIDI arpeggiator plugin in Reaper (which doesn't work very well) and not too complex. It does well. Thanks.

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Reviewed By kingfear
November 9th, 2018

I use this for not it's intended purpose, but as a random midi-gate. With proper settings, you can get only 20% notes through, or whatever you might need. It's not really meant for that so there's few caveats, as in you need to define the note length which also happens to define the frequency of the "gate". So it's not going to rally match your incoming notes perfectly.

But it's extremely lightweight, does something that I haven't found anything else to do. Except Hypercyclic which is unstable & available only as 32-bit -- also is way more random. Actually to be honest, I am not sure it even can do the same thing... but I am erring on the side of caution. I seem to recall it tends to prefer adding random notes instead of working like a gate.

But RandArp also works as a random arp, as intended. But I never use it as such.

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Comments & Discussion for CodeFN42 RandARP

Discussion: Active
9 May 2019 at 9:01am

Thank you so so much for such an amazing effect. I was like oh another arp whatever but I use Chordz and its amazing so why not give it a try and Holy #&%*@ this little plugin just boosted my inspiration and fun by a million! Thank you for making such good plugins and giving them away for free. I will donate as soon as I can.

11 October 2019 at 2:46am


I am using Studio One. I am using a MIDI track as source. Is this wrong and dumb? Am I expected to use a controller only for MIDI source. I am missing something big. I also messaged your facebook.


19 May 2022 at 5:26pm

Really love this arpeggiator, but I'm running into a really frustrating bug that I'm wondering if anyone has encountered/knows how to prevent/fix.

I use it in Reaper and have not tried it with anything else. I'll have some chords playing (to arpeggiate) on a track, and then suddenly after playing through a sequence for quite a while, it will just STOP playing like it stopped generating MIDI (I can see no MIDI is being generated), and then on the next chord press a few moments later, it will resume playing. If I have different tracks with their own RandArp instances going, it even stops those other instances. It also does it if I just have one RandArp instance in my project.

I'm NOT using note probability at all (cranked up to 100% on all instances). All random knobs are set to 0%. Velocity Fixed = 100. Rate 1/8, Type: Normal, Velocity Mode: As Played.

In Reaper, on the track I just have RandArp instance, followed by a VSTi like Serum. On the track itself, I'll have a bunch of MIDI items, one after another, that are maybe 4 bars long. It might get through like 90 bars worth, then suddenly it will stop playing all RandARP instances (but the other tracks without RandARP play fine).

So more weirdness with this... let's say I just have one MIDI item at bar 41 into my track that is two bars long. It might stop playing at bar 41.5, then pick back up playing at bar 42. If I drag the MIDI ITEM around (say if I make it span from 40.5 -> 42.5), it will always be at that 41.5 -> 42 part of the bar where the ARP cuts out. I really don't understand what's happening, and this weird problem makes this plugin unusable for me unless I bounce the MIDI out and manipulate it (btw, the bounced MIDI is missing the notes too).

22 June 2022 at 3:47am

@cstooch, you need to use ghostnotes in between your gaps. It needs to be triggered by a note all the time. Fil the gaps between your chords with ghostnotes.

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