Locking the bass to the current chord's root (or root/5th) is the safe default that ties harmony and rhythm together

The bass is ‘the most consequential harmonic voice in electronic music’ because it defines the harmony’s root motion and owns the low end. The safe default is bass-harmony-lock: play the root (or root and 5th) of whatever chord is currently sounding — when the pad plays Am, the bass plays A. This locks harmony and rhythm together and guarantees the low end supports rather than fights the chords. It is the baseline from which more elaborate bass approaches (walking bass, syncopated offbeat bass) depart, and it is the reason a clear chord-progression implies its bass line almost for free.

Examples

Over chord('<Am7 F G>'), a root-locked bass: note('<a1 f1 g1>') — each bass note is the root of the chord above it.

Assessment

What note does a root-locked bass play against a given chord, and why is this the safe default? How does it tie harmony and rhythm together?