The Joys of Cocoa (in 2024)

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The McLaren Synth Kit presents audio synthesis as the construction of a graph of audio operators (voices) with the parameters of each type of operator determined by an associated model. Voices define the code that is run in the audio thread and models hold the values that are read from the audio thread. This separation allows the audio thread code to be ensured that maniplations on the models do not block. With models safely out of the audio loop, UI interactions with model properties is straightforward and can use Cocoa idioms for manipulating property values.

At least that was the intent. The McLaren Synth Kit was released without associated GUI controls, but we believed it would be straightforward to define controls for the various models.

But we had never fully defined a Cocoa-based application that rested on the Synth Kit. We finally put it all together in our newly released application called “Synth80”.

Synth80 is a two-oscillator multi-timbral polyphonic synthesizer. This application pulls together the following features.

  • Cocoa bindings for linking Controllers to McLaren Synth Kit Models
  • Document-based application for saving and restoring presets
  • Undo/Redo facility
  • Single Document Interface document-based application for the singleton Synthesizer window

This article summarizes some of the things we learned about using Cocoa this way while developing Synth80.

Focus on Data Structures

We found that we were able to focus on modeling data more than building GUI elements. The models for our synthesizer elements (envelopes, oscillators, filters, etc) were designed first, with controls added later.

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Musical Pattern Generation with the McLaren Synth Kit

The McLaren Synth Kit (at is an Objective-C toolkit for building projects that simplify working with MIDI and sound synthesis on Linux. We open-sourced it last year and have been refining it with new features and capabilities.

Our latest features are the Metronome and a Pattern generation little-language. The Metronome hooks into to the ALSA MIDI system to provide a MIDI-clock timebase. It counts out beats and measures. The Pattern facility further abstracts the Metronome to longer sequences of events that repeat and can nest.

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GNUstep StepTalk is Alive and Well

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A few years ago, I explored the idea of writing a small interpreter for embedding into McLaren Labs applications. The concept was to extend rtpmidi or a synth application with a scriptable ability to customize controls, behaviors or sound graphs. This would help make each application very slim, but to allow extension through scripting. (This is not a very novel idea: it’s been done many times before. 🙂 )

The Objective-C execution environment (libobjc) provides many hooks that make it fairly easy to call into the ObjC runtime from an interpreter, or even to bridge Objc method calls back to an interpreter. The idea of a scritping environment to accompany a GNUstep ObjC Appplication program seemed promising and I wrote a little interpreter (based on PostScript syntax) to test out some of the ideas.

Along the way, I learned about a much more mature project in libs-steptalk. Among other things, it provides a SmallTalk-like language for extending applications or even gluing them together in the GNUstep workspace. It seemed very old, but there were some tremendous ideas in there: I wondered if I could learn enough about it to use it, and I wondered if it still worked.

(Spoiler Alert! I did and it does.)

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GNUstep Desktop – a refreshed look at NeXT/OpenStep

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There’s a cool project called “GNUstep Desktop” that brings together many old GNUstep technologies, and a few new ones, to provide an entire integrated desktop. We gave it a whirl and are pretty impressed!

GNUstep Desktop on Debian 11

It’s pretty amazing that software that began life 30 years ago is still operational and evolving, but that is the case in the GNUstep project.

At McLaren labs, we have been a fan of modern ObjC on clang, and the ObjC runtime with Foundation libraries and have been slowly learning more about GNUstep GUI and desktop. To be honest, it has been a slow learning process. While there is actually very good information about the various pieces of the GNUstep project, it sometimes seems that there are too many conflicting versions around — there isn’t a single source of truth that brings everything together. But that being said, the quality of many of the components really amazes me.

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