(Sorry I cannot follow the question format because this question is related to a problem, but is not the problem itself.) I am talking about the linear density μ that appears in this equation: v = sqrt(T/μ) .. used usually for musical instruments, where μ = m/L Now, I am wondering which value of L we use. Say that you have a string that is normally .1 kg and .10 meters long. Now lets say that u stretch the string to .12 meters to make some musical instrument. For L value, do we plug in .12 meters or .10 meters? Thanks!