(This is from experience so sorry if it's wrong but) When wind instruments are played, sometimes the notes go flat or sharp depending on the speed the player blows air into the instrument as well as the warmth of the air. When playing a string instrument, the pitch can be changed in many ways. For example, when the player places their fingers on the string depending on which part of the tip of the finger you use, the tone of the sound and sometimes the pitch, changes. Looking at the question in a different way, you can change the pitch and the range of notes you can reach on the instrument (both wind and string) by changing the note you tune your instrument to. Hope this helps!!
That is not middle school grade level.
