What is a series of musical notes that have been strung together?

Melody.

Explanation:

A melody is defined as a sequence of single musical notes that is musically satisfying. It can also be defined as the main tune of a song from the outcome of a series of notes.

These definitions of melody fit the concept requested in the question, as they both refer to a series (or sequence) of musical notes put together.

teenagers are certainly stereotyped as moody.

most people view teenagers as naturally moody and grumpy, even when this is wrong. many teens are suffering from depression but it is brushed off as "just a phase" or "that's just cause they're a teenager"