Wednesday, July 22, 2009

Max/MSP synth building

It has been quite some time since I have posted anything related to Max/MSP, Puredata or PWGL. In many respects for synthesis building I find PWGL much easier to work with, this might be a result of errors I encountered in some of the tutorials for Max/MSP. Some of the tutorials[1] for Max/MSP have errors partly due to the version they were developed for. The main issue I was experiencing surrounds the use of the umenu with the filtergraph~ and biquad~ objects. The problem with the tutorial example is the point at which the umenu item is connected to the filtergraph~ element. This connection should not happen at the right most outlet but rather should connect to the center outlet. This outlet is labeled as "Menu Item Text Evaluated as a Message" which should be connected to the leftmost inlet "a0 coefficient."

This organization of objects changes the filtergraph~ objects filter curve depending on the option selected in the umenu object. Perhaps due to changes and additions in Max/MSP there are a few missing filter types in the example on the Cycling '74 site. However, here is a complete list of filters: display, lowpass, highpass, bandpass, bandstop, peaknotch, lowshelf, highshelf, resonant, allpass. It is beyond the scope of this post to explain what each one of these filter types do. If you are interested in learning more about these filters I would recommend the book "The Computer Music Tutorial." The new filter types include resonant which is similar to bandpass but to use a definition from physics, "resonance is the tendency of a system to oscillate at larger amplitude at some frequencies than at others." And although not technically a filter allpass, functions as a bypass for the filter.

[1] Max/MSP Synth Building with Max/MSP #3

1 comment:

Brian Durocher said...

I should perhaps make one of my own amendments. The display name in the umenu~ list, to my recollection is just a list element that tells the filtergraph~ to display the equalization curve for that filter type. If you are new to equalizers or EQ for short the bass frequencies described as Hertz or Hz are at the left most side of the graph and the treble frequencies are at the far right and lay in the frequency domain of the kilohertz or kHz range.