Multiple Tracks/Channels in 1 Frequency Analyzer — In Reaper

Let's suppose you want to see the frequency content of your bass guitar compared to your kick drum. It's easy to do on a frequency analyzer (also called a spectral analyzer, or spectrum analyzer), in Reaper. And the plug-in is free 🙂

Here's how (You'll need ReaPack installed -- see resources section, below) . . .

  • Create an empty track/channel and add JS Saike Spectral Analyzer.
  • Click the route button and uncheck the 'Master send channels from/to' checkbox (see image).
  • Drag from the route buttons of whatever tracks or channels you want to analyze, to the route button on the Saike track.
  • On the first track you drag over, leave the routing dropdowns as-is (1/2 --> 1/2).
  •  The next track you drag over, leave the 'Audio 1/2' alone, but route it to '3/4' via the dropdown (see image). And so on (this is for stereo tracks/channels, but it will work for mono, as well).
Uncheck send to master

Uncheck send to master

Spectral Analyzer Routing

Spectral Analyzer Routing

Spectral Analyzer Settings

Now we have the kick as the overlay and the bass guitar as the overlay. Let's set some good settings so we can easily understand what's going on. You change settings on the spectral analyzer by clicking on a setting and dragging up or down.

All these settings can be changed to suit your particular needs, but here's a good starting point.

  • I like to set a 3 dB per octave slope so that it gives a more straight line.
  • Set the 'smooth' control to maybe 80% or so. You can set it lower if you need more detail. 
  • Set the 'Integrate' control to about 1000ms. That gives you time to see what's going on.
  • There are all kinds of visual changes you can make to the theme. You can download the way I like to set it up from the resources section below.
Bass Guitar And Kick Drum Overlay

Bass Guitar And Kick Drum Overlay

Let's take a quick look at some of the more useful controls . . .

  • Down at the bottom or the side of the frequency analyzer (depending on how far your window is expanded), you'll see some numbered buttons. Those will turn channels on and off in the frequency analyzer.
  • The 'Freeze' button freezes the display so you can study it in depth.
  • The 'Normal/Diff' button is so cool! In normal mode it shows you the frequency content of whatever audio you have routed into the analyzer. In difference mode, it shows you the differences between the signals.
  • The 'Freq/Notes' button is another great feature which lets you see the audio in terms of frequencies, or notes.

Using The Spectral Analyzer With Reference Mixes

There's another way to load up the analyzer, and I use it with reference mixes.

Open the 'Actions' menu item and search for 'loadspectrum.lua'. Double click on it and we have added the spectral analyzer as the last channel, complete with routing of our top level tracks/channels.

If you set up your reference mixes and your mix master all to be top level channels, you'll be ready to go, comparing the frequency content of your mix to reference mixes.

Reference Mix Routing With Annotations
Reference Mixes On A Spectrum Analyzer

Reference Mixes On A Spectrum Analyzer

Shout out to JSFX coder Sai'ke, who hot-rodded the already useful frequency analyzer plugin from Cockos (the folks that make Reaper).


If you want to use this plugin the way I have it set up, you can download the FX chain and throw it in your FX chains folder. Here's the path I use (YMMV) . . .

C:Users*your username*AppDataRoamingREAPERFXChains

ReaPack: extends the capabilities of Reaper via custom actions, SWS extension and more JSFX. Official download here.

About the author

Keith Livingston

Keith Livingston started recording his own music in the late '70s, on a 4-track. He worked his way into live sound and studio work as an engineer -- mixing in arenas, working on projects in many major studios as a producer/engineer, and working in conjunction with an independent label.

He taught audio engineering at the Art Institute of Seattle, from 1990-1993, and in '96, contributing to authoring several college-level courses there.

He was General Manager of Радио один (Radio 1) in St. Petersburg, Russia.

Now he spends his time recording his own songs wherever he roams, and teaching others to do the same.

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