I've been getting into this over the past couple of years too and I feel like I sort of hit a wall.

I am comfortable writing low level efficient real-time code in C (I'm an ex game dev). I understand most synthesis techniques in pretty good detail. I could probably write a book on subtractive synthesis, and I have implemented a complete functioning FM synth.

I get the fundamental concepts around DSP: Nyquist, sampling, Fourier analysis, etc.

But when it comes to sitting down and, say, designing and implementing a filter from scratch, I'm pretty well stuck. Part of it is that most of the material I've found either goes straight to heavy calculus (which I can kind of hack but am pretty rusty on) or to MATLAB (which I don't have).

Likewise, implementing a simple digital sawtooth or square oscillator analytically is trivial. Sample playback is also a piece of cake. But doing those without aliasing seems to jump from super-easy mode all the way to hardcore nightmare. All of a sudden I'm trying to understand what minBLEPs are and other stuff that feels over my head.

Any recommendations on how to get over this hump? Should I get MATLAB?