Electronically speaking, the tremolo effect is one of the simplest imaginable. Which is why the margin on tremolo guitar pedals can be so eye-wateringly high.
Tremolo is just the changing of amplitude repeatedly over time. Louder, quiter, louder, quieter, louder—you get the point. It’s not to be be confused with vibrato, which controls pitch, and is more lower, higher, lower, higher.
All this requires is an oscillator controlling the gain prop/param of the <gain-blam> element we already have in our chain. For an introduction to LFOs (Low Frequency Oscillators) see the LFOs guide.
Here, a <dial-blam> controls the gain of the LFO, which affects rhe depth of the effect. If the <gain-blam> gain is set at 0.5 and the LFO gain is set at 0.25, the subject gain will oscillate bwtween 0.25 and 0.75 (plus and minus the LFO gain value).
If you “dime” the <dial-blam>‘s slider to the max 0.5 value, the LFO will make the gain dip to zero, transforming the shimmer into a more pronounced stutter.