Concept:
The fundamental period of \( \tan x \) is \( \pi \).
For a function of the form \( \tan(ax + b) \), the period is:
\[
T = \frac{\pi}{|a|}
\]
Step 1: Identify the coefficient of \( x \).
Given:
\[
f(x) = \tan(4x - 1)
\]
So, \( a = 4 \).
Step 2: Apply the period formula.
\[
T = \frac{\pi}{|4|} = \frac{\pi}{4}
\]
Step 3: Final answer.
\[
\boxed{\frac{\pi}{4}}
\]