Mi hermano se queda quieto cuando escucha esa música.

the music

Breakdown of Mi hermano se queda quieto cuando escucha esa música.

• mi: my
• cuando: when
• escuchar: to listen

Questions & Answers about Mi hermano se queda quieto cuando escucha esa música.

What does se do in se queda? Why isn’t it just Mi hermano queda quieto?

Se makes quedar reflexive: quedarse. In this use, quedarse means to stay / to remain / to end up in a certain state.

• Mi hermano se queda quieto ≈ “My brother stays/keeps still” or “He ends up still.”
• Without se, quedar is less commonly used in this sense for people in everyday speech.
  Mi hermano queda quieto is grammatically possible, but it sounds much less natural; the idiomatic expression is quedarse quieto.

So se is needed because quedarse quieto is the standard, set phrase for “to keep still” in Spanish.

What’s the general difference between quedar and quedarse?