Audio Filter Band Pass / Band Reject - missing


TD 099 - Build 2022.32120

1) the bug
missing Parameter for this kind of Filter … there exists only one (named Filter Cutoff) … but for a Bandpass there needs to be 2 (low Border / High Border).

these 2 possts adresses the problem.
Audio Filter CHOP incorrect filter desc in docs (2019!)
Audio filter questions (2017!)

2) Workaround

anyproblems (beneath cooking time) when using first a a lowpass filter as the upper border and then a Highpass filter for the lower Border ?.

thanks for your support

The typical implementation of a band-pass filter in an analog synth is achieved by mixing the high-pass output with the low-pass input which both share the same cut-off. I would strongly disagree that two cut-off parameters be required on this CHOP.

In this case, a high-pass and low-pass filter in series is exactly what you are looking for.

maybe that is ok for someone with that background … (I do not have this). For me at first is relevant what the Developer or the Product-Owner decided what “Bandbass filter” stands for and how to implement it.

let`s have a look at

Band Pass bandpass - All frequencies between the Low and High Cutoff are passed through. …after reading this … where is the “Low Cutoff” and where is the “High Cutoff” ?? there exists “only” one => Filter Cutoff(hz) … hmmm

maybe there should be an update on the document: but
Yeah, the oversight on the band-pass is unfortunate. Right now the Filter Cutoff Freq is just the center frequency and the Roll-off goes out from there in each direction, so not a useful band-pass. In our todo list! (Audio filter questions)

I dont want to blame someone here ... Its just a hint of, “there is something wrong” …please fix it !

Wikipedia (Audio filter - Wikipedia) → what is not the truth of all , sometimes a good starting point to get some insights in other, unknown or less known Domains

A band-pass filter passes frequencies between its two cutoff frequencies, while attenuating those outside the range. A band-reject filter attenuates frequencies between its two cutoff frequencies, while passing those outside the ‘reject’ range.

OK that doesn`t mean we need two Parameters … just one that is in the center of the range so the User has to do some math… do I want as User do such math … surely he can … but Software should support the User to keep him focused not to do such things …

so for me as a User and a good UX (User Experience) I would vote for 2 Parameters … that get actived and descripted based on what type of filter a User chooses …

Overall: TD is a dgreat peace of Software with a very good UX to me !!!
happy coding
Peter B.


This bug and mismatch between the documentation and the OP are misleading.

It seems the AudioFilterCHOP was left half-finished

I usually workaround this problem with one high pass and one low pass filter in series but why is the doc referencing to a low and high frequency cutoff ?