Check octaves in first position, alternating across three, and four strings. Open strings will be at the lower octave across three strings, and at the upper octave cross four. Contriving a completely arbitrary notational protocol which is applicable only in this instance, in which a capital letter denotes an open strin g and a small case letter indicates a fingered note, this would give you E-e (6th and 4th strings); g-G (6th-3rd); A-a (5th-2nd); b-B (5th-2nd); D-d (4th-2nd); e-E (now 4th-1st); G-g (now 3rd-1st). This is a good check because in the process you are constantly cross checking newly introduced variables (i.e., open strings which have not yet been checked) against an expanding array which has been brought into homogenously correct intonation- assuming, that is, that your instrument is accurately fretted.
You can then continue by moving up to the seventh fret and checking octaves of the seventh frets across the fingerboard against the adjacent lower string (that would be eighth fret on the 2nd string).
Check unisons. There is the standard novice check of fifth frets across the fingerboard against the adjacent upper string (4th fret on 3rd string), but also the 10-10-9-9 check. The tenth frets on the 6th and 5th strings are unisons with the open 4th and 3rd strings; the ninth frets on the 4th and 3rd strings are unisons with the open 2nd and 1st.
It is octaves and unisons that will be most prominent when out of tune; the foregoing process checks all strings against a variety of open and fingered comparatives in which such "out"-tonations are likely to occur. Provided everything is verified to be correct, the routine can be gone through quietly, in a matter of seconds. If there are obvious fretting inaccuracies in your instrument (which are not uncommon) , then you are probably "attuned" to them, and know which ones to let stand, and which need to be brought into correct intonation- which is a complex which can vary according to the exigencies of whatever is the piece you are about to play. The inaccuracies you may let stand can be compensated for by slight bends, or by applying and holding in stasis a longitudinal vibrato at one or the other extreme end. Sometimes you may even be able to do this with one finger while engaging the others in simultaneous action.
The first phase of the check procedure (i.e., the "first-position-octaves-alternating-between-across three -and-across-four-strings" check) can also be replicated using perfect fifths as a check interval instead of octaves. In this case, the alternation would be of fifths on adjacent strings with fifths across three string, or (low to high, and invoking the same notational protocol) E-b; g-D; A-e; c-G; D-a; e-B; G-d; a-E; B-f#.
The caveat with fifths is that the guitar is (supposedly) an equal-tempered instrument. This means that the fifths you have to listen for are equal tempered fifths, and not "perfect" acoustic fifths. The equal tempered fifth will be just slightly flat in comparison with the pure fifths in which singers, bowed and other fretless string players, trombonists, and noted slide whistlers and kazooists can freely indulge. The difference, as I said, is very slight, but as a replicated procedure, it is possible thereby to introduce an error which will add to its discrepancy at every step, until it becomes quite noticeable. So, best not to do the fifth check until you've already done at least the octaves.
Thus "equal-tempered differential", by t the way, is why the harmonics check for unisons between fifth fret harmonics and seventh fret of adjacent higher string harmonics (except for the 3rd and 2nd strings) is problematic. The fifth fret harmonic gives you the note you want; the seventh fret does not. The seventh fret harmonic is an acoustically pure fifth. Therefore, The unison between the two harmonics, if this check is used, should not be exact. The fifth fret harmonic should be just barely higher than the seventh fret harmonic on the higher string.
Further caveat: Once you've gotten your guitar perfectly in tune, supposing your guitar has no fretting displacement errors, you still may not be satisfied. You may play major chords and find that the thirds sound as if they are too sharp. This is because they are too sharp. The difference between a pure major third and an equal-tempered major third is greater than is the difference between a pure fifth and an equal-tempered fifth. Therefore, most guitarists will still fiddle around with their tuning even after they've gotten it "perfectly" in tune. The "temperment" they are applying at this stage, is no longer one founded on abstract objective theory, but one of empirical subjective alignment with oneself. It may be discussable on a factual basis, but after the mechanical phase of the procedures alluded to above, what happens is not necessarily an intellectually calculated process. It is , rather, one carried on by the agency of an "instinct" which is actually a well internalized data set based on experience, which has become manifest in autonomous responses. One need not parse exactly why one may soften a harsh equal-tempered third in one particular chord while letting a less than exact octave or unison stand somewhere else, one just "does" it- though if pressed, most people at this stage could probably tell you why. And, exactly which imperfections are corrected and which are tolerated, will likely change according to the features of the situation into which one is about to enter- the characteristics of the piece or instrumental combination coming up.
One finds oneself developing ones own little repertoire of tentative chord successions, intervallic juxtapositions, arpeggios, phrases, etc. that one invokes in order to test for the intonational alignment that is optimal for the particular approaching juncture. To the extent that one derives any satisfaction from this very process, or that it may catch the attention of anyone nearby, it is interesting to note that this is the very origin of "preludes" as a musical form in and of itself. It was born in the foolin' around that lutenists used to do while getting tuned up, when they noticed that it was not only a practical necessity (the moreso in that this was an age in which lutes had adjustable frets to be attended to), but it was also an opportunity for them to sneak in something impressive that would be engaging to the interest of their potential audience. There is one such account written up by an observer of Francesco da Milano's appearing as a performer at a sumptuous banquet for the higher echelon of society, in which it was noted that he managed to catch the notice of all noble attendees' in the midst of their post prandial frivolity with just the experimental sounding of three chords before constraining them to face him, whereupon he proceeded to entrance them all with the instrumental flights of fancy he was able to produce. What a touch he must have had.
Last edited by guitareleven on Thu Nov 15, 2018 4:11 pm, edited 1 time in total.