Two infinite loops written in sequence can never both run, because the first loops forever and the second is never reached

A classic beginner surprise in Sonic Pi (and any single-threaded language) is writing two loops one after another and expecting both to sound. They cannot: the program runs top to bottom, reaches the first loop, and that loop runs forever — so control never reaches the second loop below it. This is not a bug but a fundamental property of single-threaded execution. To make both play, you need concurrency: two programs running simultaneously, one per loop. The hard part of concurrency is managing shared mutable state; if you avoid that, concurrency itself is not hard — which is what makes it teachable to children once the tool provides the right abstraction. Recognizing why the sequential version fails is the conceptual prerequisite to the live_loop solution.

Examples

A student writes loop {play drums} then loop {play bass}; only the drums sound, because the drums loop never ends and the bass loop below is never reached.

Assessment

Explain, in terms of single-threaded execution, why two loop do...end blocks in sequence can never both play. What is needed to make both run at once?