Get in Tune

The first and most important step when recording a band is making sure each instrument is in tune.  For the most part, each musician has a handle on their own instrument and how to keep it in tune.  Some use a digital tuner, via either an amp or a pedal, but some still prefer to tune by ear.  As an engineer, hearing an instrument out of tune is one of the best ways to bring a session to a stand still.  Recording or rehearsal stops while the guilty player fixes the problem and valuable time is wasted.  The ability to hear this problem isn’t exclusive to those with a “trained” ear; but it is always obvious and very annoying.  Actually, as an engineer, you’ll most likely notice it before the musician because of your objective point of view.  One technique anyone can use, whether you play an instrument or not, is tuning harmonically. 

Tuning an instrument harmonically involves a bit of physics that I won’t delve into right now, but if you can hear “beats” between two tones (which anyone can) you can tune any instrument this way. 

When you pluck a string, it will vibrate at its fundamental frequency (giving the string it’s pitch) and harmonic frequencies (giving it’s timbre).  By lightly touching open strings at particular intervals (5th^, 7^th, and 12^th, frets) you can isolate these upper harmonics.  For instance, lightly touching the 5^th fret on the lowest string of a guitar should produce the same harmonic note as lightly touching the 7^th fret on the string above, which would be the A string.  If these two tones are in tune and rung out simultaneously, you will not hear an audible difference in pitch (i.e. no beating between notes).  This means that the two strings are in tune with each other and you can continue the process down the strings.

The difference of .5 Hz between two tones 

If these two tones are out of tune, you will hear an audible “beating” between the notes, signifying that there is a slight difference in frequency.  If the frequency doesn’t match up you will hear beating as a result of amplitude modulation between the two tones.  The further away the two tones become, the more out of phase they become, hence the more out of tune and the faster the beating between the notes.   

 

But as the frequencies approach each other, the beating slows and eventually disappears, creating a unified note.  This is when the two strings are in tune with each other.

Difference of 3 Hz, audible "beats"

I think this is the best way to get an instrument in tune, given that there is a correct reference note, but there are some detractors, albeit very picky ones.