I have made a polyphonic synth in vanilla PD which is pretty great but it has a lot of aliasing. When I start to implement oversampling I quickly run out of processor time and start getting dropouts.

I have never used externals.

If I use filters from a library like iemlib, will this make my synth more efficient?
If so I will look for libraries with anti aliased oscillators and nice sounding filters....

Or is the efficiency just the same, and some people just find externals more convenient?

This really depends on what you're doing. Why not use the native filters, [lop~] for example, or [biquad~] if you know how to calculate coefficients?

@nuromantix [biquad~] is useful...... and the ggee library has externals for converting gain, q, frequency to the necessary coeffients that @alexandros mentions.

David.

@nuromantix yes anything written in pure data will be much slower than the equivalent algorithm in c, compiled as an external.
As an example every time something has to travel along a cord, that involves a function call whereas in c an assignment or memory access compiles to a simple cpu instruction.
Also, every computation in pd is done at runtime, whereas when you compile something the compiler can optimize so many things.

@alexandros
I'm using your "multifilter" abstraction among other things. sounds great, thank you! lop~ isn't really very exciting for a synth and not much use as a brickwall for antialiasing either.... biquad~ maybe I need to learn about
@seb-harmonik-ar
Thanks for the nice clear answer. I will try out some externals to try and reduce CPU load a bit.