I applaud the author for wading into analog electronics. Pretty much everyone nowadays would just put a timer on a micro and be done in 2 minutes. No fun in that. There is something to be said about the minimal elegance of purely analog designs, and a special rewarding feeling for wrangling electrons in their native habit rather than their boxed up binary bins.
I think it depends on the ecosystem. It's true much of the "maker" community tends to embrace whatever solution is the cheapest, fastest and easiest to get something working out the door, but on the other hand, the DIY synth community tends to be the opposite (in my experience at least), favoring simple schematics and "back to basics" building, even sometimes going as far as trying to skip any sort of prebuilt ICs.
Transistors were, for some reason, seemingly unknowable to me. But I made a kind of "transistor playground" [1] based around Forrest Mims III book [2] and then enjoyed playing with them.
[1] https://imgur.com/a/dChq4AZ
[2] https://archive.org/details/forrest-mims-basic-semiconductor...
Edit: actually, I had forgotten it was a transistor logic playground for I made for creating logic gates with transistors. Based on another Forrest Mims book: https://archive.org/details/engineersmininot00mims
I've got dozens of them in my electronics drawers I don't really use anymore since ESP32 dev boards are so cheap and capable for home projects.
At this cost for a hobbyist it's just hard to beat. It can be anything you want it to be in a few lines of code.
I personally write Rust for it, not Arduino C++, but it would work just the same.
Granted, you can almost get a microcontroller for that price…
Kind of mind-blowing. 24mhz 32-bit computer for under a dime.
But you'll learn more about the analog-ish world and not need to deal with SMD if you go the 555 route. And it'll save you power vs the astable monovibrator with NPN transistors.
Make has a really nice little book where they walk you through some simple projects on a breadboard with 555s, transistors, etc. https://www.amazon.com/How-Use-Breadboard-Make-Handbook/dp/1...
For £3.50 you can get an ESP32 module with WiFi and Bluetooth (e.g. https://thepihut.com/products/esp32-c3-mini-development-boar...)
(A regular Arduino board might still be the best choice if you're just learning/tinkering though)