Transients

A transient is the very first burst of a sound - the quick "snap", "click" or "thump" at the beginning. When a musician hits a drum, claps their hands, or plucks a guitar string, the sharp attack you hear right away is the transient. It usually lasts only a tiny fraction of a second, but your brain uses it to recognize what made the sound and how hard it was played.

Transient shaping is changing that attack without changing the whole sound too much. Turning the transient up makes sounds feel punchier and more energetic, like a drum hitting harder. Turning it down makes sounds softer and smoother, like moving a drummer farther away or wrapping the drum in cloth. Transient shaping then, allows you to control how aggressive, sharp, or gentle sounds feel in your song.

Besides the regular envelope generators for amplitude and filter, there are two main ways to shape the transients on a track;

1. Using the third oscillator in "click" mode; the third oscillator's sine wave starts at a 90 degree phase, meaning that the waveform starts at full amplitude. This causes a "click" (due to the speaker being pulled immediately to "max volume" rather than ramping up with / riding the start of the sine wave). This simple track can add punch to kicks and other percussion, as well as regular synthesised instruments.
2. Using the track's compessor in downward compression mode (with fast attack and very low threshold); this causes a track's sound to start off normally, then sharply reduce the volume of the anything that follows. This creates a comparatively louder transient than the rest of the sound.

If your sound uses reverb, be sure to dial in a suitable reverb pre-delay (15/A7/rv.P.d on the Song's FX page) that gives your sound time to play its transient before its reverb signal starts blending in and - potentially - obscuring/"drowning" the sound.