To demonstrate stability we can simply bypass using a reference frequency and get a more simple equation:

A strobe tuner shows the difference between a reference frequency and the musical note.

This process only measures the difference between the unknown frequency and the reference frequency, which must be determined by some other method.

Some phonautographs included a tuning fork or other means of simultaneously recording a known reference frequency.

Do Pitch class mapping with respect to the estimated reference frequency.

The second term is a sinusoid at twice the reference frequency, so it can be filtered out.

The divided signal and the reference frequency are fed into a phase comparator.

This allows the synthesis of frequencies that are N/M times the reference frequency.

When the cache is full and requires more room the system will purge the item with the lowest reference frequency.

An oscillator was used to hold the reference frequency for comparison to the received signal.