Isn't always nice when an exercise feels more like music and less like an exercise? I think so.
And so SightRead.org now includes pad playback: background chord progressions that play along with the rhythm exercises. It adds harmonic context, hopefully without getting in the way.

How it works
Enable "Synth pad" in the Settings panel. When you play an exercise, chord progressions play as sustained synth pad sounds in the background. Tip: combine this with the 4OTF metronome and turn up the subdivision volume for extra... oompf! Try it.
Each chord plays for exactly one measure, synchronized with the metronome. The pad stays in sync even when time signatures change mid-exercise like 4/4, 3/4, 6/8, etc.
What you hear
The pad uses a soft synthesizer sound with attack, release, and echo effects. It's designed to sit in the background, providing harmonic context without competing with the rhythm.
Chords are generated automatically using common progressions (like I-V-vi-IV) in a randomly selected key.
Happy sight reading! 👀