# Add a pitch knob to the Convolution Reverb plugin
**URL:** https://qa.fmod.com/t/add-a-pitch-knob-to-the-convolution-reverb-plugin/23467
**Category:** FMOD Engine
**Created:** [October 14, 2025, 11:46am UTC](https://qa.fmod.com/t/add-a-pitch-knob-to-the-convolution-reverb-plugin/23467 "2025-10-14T11:46:06Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@vincentoliver](https://qa.fmod.com/u/vincentoliver)
#### Post date: [October 14, 2025, 11:46am UTC](https://qa.fmod.com/t/add-a-pitch-knob-to-the-convolution-reverb-plugin/23467/1 "2025-10-14T11:46:06Z")
Hey all,
I’m working on a game where rooms change sizes while you’re in them. I’d like to be able to use a convolution reverb and resample the IR so it speeds up/slows down, giving the impression of a room getting bigger/smaller.
I thought the easiest way would be to create a custom plugin by copying the code of the Convolution Reverb and slapping a pitch knob on it. (If Firelight allow you to poke around in there)
I’m not a coder - I’d hire one - but I’m wondering if this is a) the best solution to my problem and b) feasible.
Thanks!
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### Author:  [@Leah\_FMOD](https://qa.fmod.com/u/Leah_FMOD)
#### Post date: [October 20, 2025, 6:51am UTC](https://qa.fmod.com/t/add-a-pitch-knob-to-the-convolution-reverb-plugin/23467/3 "2025-10-20T06:51:55Z")
The Convolution Reverb plugin unfortunately doesn’t support changing the pitch of the IR. Depending on the specifics of your game, you could potentially use a series of different discrete “room size” IRs, or a number of IRs that move from/to various sizes/pitches to, to emulate this effect.
> [@vincentoliver](#):
>
> I thought the easiest way would be to create a custom plugin by copying the code of the Convolution Reverb and slapping a pitch knob on it. (If Firelight allow you to poke around in there)
It also isn’t possible to copy/modify the source code of the FMOD Engine effects, and it likely wouldn’t be quite so simple as slapping a pitch knob on it. However, a custom DSP plugin effect using FMOD’s DSP API would definitely be what I’d recommend looking into if you can find a convolution reverb and pitching/resampling algorithm that suits your needs.
Alternatively, if you have access to Max & RNBO, you may be able to use an effect created in that instead - FMOD’s Core API examples contains the “fmod\_rnbo” example, which demonstrates how to integrate exported RNBO code into an FMOD effect.
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### Author:  [@vincentoliver](https://qa.fmod.com/u/vincentoliver)
#### Post date: [October 23, 2025, 1:56pm UTC](https://qa.fmod.com/t/add-a-pitch-knob-to-the-convolution-reverb-plugin/23467/4 "2025-10-23T13:56:24Z")
> [@Leah\_FMOD](#):
>
> Max & RNBO
I did not know about this, thank you!
The game is all about stretching and squashing and every single room gets stretched to varying degrees so, unfortunately, a discreet bank of IRs would be quite out of the question