I would also like to express my gratitude along with amazement at the pace you've managed to keep up. I got caught up with finishing a lab project and now with exam preparation. However, I'll be done with exams on Friday and have a month before my next project starts, time which I was planning to fill with maths. I've currently worked the book up to the end of chapter 4, but still need to start digesting your posts on the subject.

Thinking about this material daily and reworking basic category theory has illuminated and solidified many of the concepts. Your perspective has really helped in this regard. I've finally got a good grasp on adjoints and all of the maths I'm encountering seems an entire step or two easier in the uptake. I'm also starting to get a feeling of how one could effectively use monoidal categories. When browsing some of your work before this course, I had trouble understanding exactly what was going on when tensoring and couldn't divorce the idea from categorical (co)products. The lead-up via monoidal preorders has changed my perspective on what these structures are.

I would really appreciate your thoughts (particularly big picture stuff) on the networks from chapters 5 and 6. Additionally, a compiled list of references for further study in some actionable order at the end of the course would be really helpful. The lists on your website have proved invaluable for my studies.

Regarding music recording: I'm no expert, but I've messed around with home recording and some DJing from an early age. A short list of what you'll need based on your request for electronic and live music:

- Hardware:

1) You'll want some sort of USB audio interface. This is essentially an external sound card that includes the requisite input/output channels and allows you to record latency free (the sound card on your computer is probably to slow for this). These come in a variety of configurations and price ranges. I don't have any concrete recommendations, but you will want something that has a MIDI input as well as one or two audio jack/XLR (for microphone) inputs along with headphone outputs. You should be able to find an all-around solution for around 200$.

2) Midi Controller: If you don't already own a keyboard with MIDI output, I would highly recommend getting such a thing. Even if you don't play piano, you should have some device that's more tactile than a computer keyboard and mouse to tap out rhythms and melodies ect. You can get bare bones MIDI keyboards that only cover 2 or 3 octaves (they can sit on your desk) fairly cheaply (under 100$). If you want weighted keys it gets more expensive.
Alternatively, if you are more into rhythmic expression, there are a plethora of pad-based MIDI controllers (imagine an array of square tappable rubber pads) out there, also available in basic options for around 100$.

3) Microphone: Most instruments like digital keyboards, guitars, basses ect., will have audio jack outputs that you can plug directly into your USB interface or if you have a guitar amplifier you can output that sound into your computer. If you want to record voice, ambient sound or acoustic instruments you will need a microphone. It's worth getting a decent one. I have the Rode NT1-A which comes in a practical starter kit including pop-shield, cradle, and cable. This would set you back 150$

4) Cables and adaptors. Rule of thumb: There will always be one essential piece missing, no matter how much you've considered things before ordering. Maybe apply some category theory.

- Software:

Here things get a little complicated. As far as I'm informed most people doing recording work either in Logic Pro if they're on Mac or Cubase if on Windows. Imagine the software platform as a framework that you bolt plug-ins on as desired. Most of the specialized functionality professionals use comes from these. The base software will, however, cover most of your needs and there are many free plug-ins online. I've personally used Cubase. It's a little intimidating to get set up (audio drivers), but after that, it's not too difficult. I'm sure there are tutorials on youtube. I recommend you get full-fledged software that's in standard use.

The way these software platforms work is that you have a timeline where you can edit your tracks (eg. cut, paste, ect.). There is a strong division between audio tracks (e.g from a microphone) which are handled in waveform and midi tracks, which are just a pitch plus an intensity and duration. Audio will sound like whatever you piped in. You can layer effects on top of this (e.g reverb, delay, compression, (co)equalizer :). The software comes with a basic suite of standard effects and tools. For more specialized/refined ones (e.g good guitar amp emulations) there are plug-ins.
MIDI tracks, on the other hand, has to be 'instrumentized' in order to sound. The software uses so-called VST instruments for this. These can either be synthesizers (compute sound based on algorithmic wave-form generation) or sample-based instruments (take recordings of an instrument's sound and adapt it to your MIDI track). Generally, the VST instruments included in the base software aren't satisfactory. Good synthesizer plugins can be found for free or cheap online (only requires programming to produce) while good sampled instruments (e.g symphonic instruments) get really pricey since people have to go out and record thousands of samples for each instrument. The standard plug-in used by composers ect. is called Native Instruments and costs 500+, but can produce orchestral tracks that are for the most part indistinguishable from an actual recording.

But again, a standard software will get you started and once you mess around and find your work-flow you will know what you need additionally. If you want to perform you're composed electronic music creatively in a live setting, that's a separate can of worms.

That concludes my mini-lecture. Hope this gives you some idea of what you're in for. All in all, I would say getting into the software aspect is on the level of learning basic photoshop or equivalent. You will only make use of a small subset of the features. And there will be tons of resources out there to help get you started with basic work flows. Most of the fun comes with messing around. Feel free to ask any further questions. I should get back to studying.