Simply explained, DSP takes real-life signals that have been digitized and manipulates them mathematically by adding, subtracting, dividing, or multiplying the signal path. You find it in the form of a filter, ADSR, or delay effect in your soft and hardware synths, or modulars.
Developing DSP on a sophisticated level obviously not only requires the mathematical and coding aspect but also you need to have an ear for music and a sense of art. There are only a few people out there capable of giving an understanding of DSP in a clear and accessible way as Vadim Zavalishin does.
In this video, the inventor of REAKTOR Core and in-house DSP developer at Native Instruments dives deeper into the art of Digital Sound Processing. During a talk that was recorded at the SRH University of Popular Arts in Berlin earlier this year, Zavalishin explains how he made a lot of REAKTOR ensembles sound better by using analogue-style filter modeling, and goes deep into its sonic details that were added to REAKTOR’s 6.2.2 update.
Also highly recommended and a bit shorter in length is Vadim Zavalishin’s talk at Native Sessions: Patch. Play. Build. Back in 2016. Here he gives a detailed hands-on explanation of modifying a filter in Core.