Hi everybody! First post for me here and I also must confess I'm a newbie with PD but the interest in this patch is precisely what drove me here, so hope this won't sound too lame. I've got an idea for a patch but no clue as to how to work it out, so I thought this could be the right place to ask for help.

Basically I'm in need of a resonant filter that can be played with a midi keyboard.

For those of you familiar with ProQ-3, just imagine you were to pick a frequency, narrow its Q to the extreme and boost it all the way up. As you'll know, ProQ-3 has a keyboard underneath the main controls to show you what note that frequency corresponds to: this is precisely where my needs are.

Imagine you could raise those peaks by pressing a midi key and you could have it polyphonic, so that you could underline a "chord" or a melody within the spectrum of a given audio file or - even better - an incoming audio signal/content.

How could such a patch be designed? I've been told I could use the [mtof~] object and I thought maybe I could start from a multiband parametric eq. patch and assign a [mtof~] to each band but, again... I confess I would barely know how to start with this. Maybe there's already anything like that available? Thanks in advance for the support to those who will chime in!

Check out this https://github.com/alexdrymonitis/filter_abstractions
both [omniFilter_abs~] and [multiFilter_abs~] can create a resonant lowpass filter. Getting note on and note off messages in Pd can be done with the [notein] object. Just create one and right-click on it, then click on help in the pop-up menu.
As for [mtof~], you're right, you need that to convert MIDI notes to frequencies. There's also a control-rate version, [mtof], without the tilde.

Adding on to what @alexandros wrote, you could also try [vcf~] which is a vanilla object. It has both bandpass and lowpass outputs, and you can vary q. I've chained 3 in series for a stronger effect.

Also, I recommend taking things one step at a time and verifying you got things right before continuing to the next step. It could be;

• Verify that you are getting MIDI input into Pd and that you understand the data coming in.
• Check that you can convert MIDI pitch to frequency, which is what the filters will need
• Maybe start with a mono patch with just one filter
• Then tackle stereo and/or polyphony

@Vorg [reson~] from the cyclone library is a good bet for your filter needs.