Custom DTMF generator

This plug-in is a generalisation of the built-in DTMF generator, allowing a user to generate DTMF tones not present on a telephone’s dialpad.

Usage is exactly the same as the original DTMF generator, but instead of specifying a series of digits to play, two arbitrary frequencies may be entered.
As with the original, the volume is set to 80%, and allows a settings of tone duration and an optional period of silence after the generated tone, which can be useful when tone sets are being generated.

I made this plugin because I needed to generate some DTMF tones to demonstrate an aviation SELCAL tone set, but I’m sure there are other uses. Hopefully someone uses it!
custom-dtmf.ny (1.33 KB)

Thanks for your contribution aliask.
I don’t think this plug-in is sufficiently mainstream to be part of the standard Audacity bundle, but no doubt it will be useful for some, so I’d like to put it into our ‘official’ on-line library

As you will see in the "Tone Generators" section, there are already a couple of DTMF plug-ins.

Could you write a bit of text in similar fashion, to describe your plug-in. In particular, it needs a brief description of the overall effect, which in this case should include the fact that it creates a single beep rather than a sequence, and a brief description of each of the controls. Don’t worry too much about formatting, it’s just to help me get the description right and I’ll sort out the formatting on the wiki.

I think the links that you provided on GitHub will also be useful, so that information can go in.

Some comments about the code:

It’s recommended that new plug-ins should conform to the most recent “version”, which is currently version 4. This doesn’t make much difference in this case other than the “;version 4” header.

There is now an “;author” header for the name of the programmer.
The “;info” header is no longer used and is just treated by Audacity as a comment. The “;author” header may be used if effects are sorted into groups (

More info about headers here:

The correct link for the GPL v2 license is:

For LISP based languages, there are certain conventions for indentation and new lines. This becomes quite important for readability with larger programs. There’s a good guide here:

I’ve made these tweaks to your plug-in in this version, so if you’re happy with it, this is the version that I shall upload to the wiki.
custom-dtmf.ny (1.42 KB)

Thx, man. Definitely one I don’t have any use for now, but I’ll keep it in my toolbox. Dual tones are still used for all kinds of selective call systems and I’m sure it’ll be of use one day.

No problems!

Awesome. I agree it’s not really a common use, so glad to have it included on the Wiki rather than in the Git repo. Cheers!

Custom DTMF generator
Generates a single DTMF tone of customisable frequencies. Useful for generating other telephony DTMF tones, and SELCAL tones for radio communication.

  1. Tone Duration: [1 ms - 10000 ms (10s), default 100ms]
  2. Silence Duration: [0 ms - 10000 ms (10s), default 100ms]
  3. Frequency 1: [1 Hz - 10 kHz, default 425 Hz]
  4. Frequency 2: [1 Hz - 10 kHz, default 25 Hz]
  5. Volume: [1% - 100%, default 80%]

Thanks for the updates, I’m happy for these to be put up on the Wiki as-is.


Thanks for making this, it is a life saver! I’ve been generating custom DTMF since 1996 when Cool Edit 96 had it out of the box. I use Audacity for most things but always downloaded Cool Edit’s latest bloatware to do this simple task when needed. The fact that this is NOT part of the regular Audacity install is mind boggling to me, it’s very useful for me for creating quick tones on the fly (I’m a phone phreak, so the old MF bluebox tones are a quick example, but there are various DTMF tones that are used for all kinds of things – as of right now I was demoing Emergency Alert System’s tone that you hear before a warning is flashed on tv/radio etc, I wanted to whip it up quick, don’t have Cool Edit on this computer, googled audacity custom DTMF and landed here). IMHO This should just come with the Audacity installation as a default thing. Sad that Cool Edit has had it for 22 years, and it’s only been an Audacity plugin for the last year or so.

Audacity has included a DTMF generator for many years:

This is true, but the ability to create your own DTMF of different frequencies has not, which Cool Edit has offered since their release.

Arguably it has, but not labelled as such.
Audacity has the “Nyquist Prompt” effect which can be used for generating tones.
For example. this code will create a tone containing two frequencies, 1000Hz and 230Hz

(mult 0.4 (sum (hzosc 1000)(hzosc 230)))

How it works:

  • (mult 0.4
    scales the generated sound. As we will be adding two full-scale sounds, the result will have a peak amplitude of 0.8.
  • (sum
    Adds the generated tones
  • (hzosc 1000)
    Generates a 1000 Hz sine tone.
  • (hzosc 230)
    Generates a 230 Hz sine tone.