The Key Signature page. Paragraphs in this page are: Why Key Signature Key Signature table Tips Why Key Signature In the Modes-Scales page, we learned that the scales, being Modes applied on a specific note most often need accidentals in order to maintain the interval order intact. We also saw that the Natural Genre produces different Natural Scales. C Ionian (Major), D Dorian and so on. Finally, we saw that different Scales from the same note have different accidentals. Let's see again 3 different Scales: C Major is the Natural Major Scale. G Major needs one sharp at the 7th note. Let's try a perfect fifth under C. E Major needs 4 sharps. Let's think. G is a perfect 5th on top of C. Let's try a perfect fifth under C. F Major needs one flat in the fourth note! See next example! Major Scales 5th Perfect around C Natural Major Scale. Forward: G Major is a 5thP above C Major and needs to raise the 7th note (F). C has F Natural, so G sharpens it. F Major is a 5thP below C Major and needs to lower the 4th note (B). C has B Natural, so F flattens it. Backward: C Major is a 5thP above F Major and needs to raise the 7th note (B). But F has Bb, so C cancels it! C Major is a 5thP below G Major and needs to lower the 4th note (F). But G has F#, so C cancels it! Generic rule despite the accidental type: If X Major is a 5thP above Y Major, keeps Y Major's notes but raises its own 7th. If X Major is a 5thP below Z Major, keeps Z Major's notes but lowers its own 4th. Now let's see the following example: Major Scales 5th Perfect around C with Key Signatures. The  key signature is marked after the clef and refer to all the relevant notes in any octave. When the key signature is for some reason "cancelled" inside the score, this action is valid only for the current bar only for one voice and only for the specific octave. In the Tonal Musical System (which defines the Baroque era) the need to specify the tonal harmonic center produced the secondary need to mention which notes would be altered even before the musical piece began. The tonic centers (represented by the major scales) form a classification related to the number of accidentals needed to produce a specific tone center. In this classification, the "close" tones are not the ones that are close as an interval, but rather the ones that differ less accidentals, therefore have closer key signatures. C Major Tone is closer to G than to E, even though E is a 3rd Major tone distance (smaller than 5th Perfect), because it is closer regarding key signature to  G (1 accidental) scale compared to E scale(4 accidentals). The classification of key signatures is based on a 5th Perfect (or 4h Perfect depending on orientation) climax, extending from C (natural major scale) in the middle into 2 directions, the sharp direction up to C# and the flat direction up to  Cb, forming 15 tonic centers represented by all the real scales that exist in this system. Q: But the system is 12 tone, how can 15 real scales exist? A: 6 scales are harmonious in pairs: B~Cb, C#~Db, F#~Gb. But their tonic centers exist nevertheless. All key signatures are based on the Major Mode and secondary refer to the relevant Minor Mode. A relevant minor Scale is always a 6th Major above (or 3rd minor below) the Major Scale that defines the key signature for both. Q: Why is the Major Mode more important in defining the key signature classification? A:  Primaryly Because the Major mode forms the major harmony. Back in the Tonal Musical System beginnings, all modes submitted to two modes that carry within them harmonic qualities of the Major and the Minor. The primary Major Mode is the former Ionian and the primary Minor Mode is the Harmonic Minor which derives by by sharpening the Aeolian Mode's seventh note. The Minor Tone exists in three instances, Natural (former Aeolian), Harmonic and Melodic. Every instance though, is considered as the 6th grade of a Major tone because it derives from there. Further Tonal Music System issues will be covered in the Tonal Music System page. The Major (Ionian) Mode is more straightforward, exists in only one "instance" and its natural scale (C) is the one we always think as the first note of the western music's note pool. It's therefore more practical to base the key signature classification on the Major scales. 1 Key Signature example and the Scales defined. As you can see, 1 key signature defines a Major Tone and the relevant minor. Key Signatures are very practical considering any Tonal environment because it's very easy to figure the tonality of the musical piece. The minor mode is characterized by the accidentals that add a "harmonic" minor quality and is therefore very easy to distinguish. So, now, in the following paragraph we will see all keys and relevant Scales. Key Signature table Sharp Key Signatures The Table starts with the C Natural Major Scale and continues by ascending 5thPerfect steps. As indicated, the sequence can easily continue on and on after C#, giving us scales with double sharp key signatures, first being G#. Flat Key Signatures The Table starts with the C Natural Major Scale and continues by descending 5thPerfect steps. As indicated, the sequence can easily continue on and on after Cb, giving us scales with double flat key signatures, first being Fb. Let's now see a unified table: All Key Signatures from Cb to C# Here, all  scales are organized in a single Table. From Cb in the bottom, all scales go up a 5th Perfect up to the top. C is in the middle. It is clear what every scale does in a continuous procedure: Every scale raises its seventh compared to the lower 5th scale, but lowers its fourth compared to the higher 5th scale. As G Major raises its 7th note from the natural note pool making it sharp, the Gb Major raises its 7th note from the all flat pool, making it natural. D has 2 sharps (F# C#) Db has 2 natural (F C) and all the other flats. Tips After all these tables, we may ask ourselves "How am I supposed to remember all this? The answer is By Heart. Through much use, frequent score reading and some initial "mathematic" thinking, it gets easier as time passes. All scales can be constructed by modes: Horizontally: Think the intervals that generate the modes: Major=TTsTTTs Natural Minor=TsTTsTT Vertically: think the note distances from the base note: Major=1P 2M 3M 4P 5P 6M 7M Natural minor=1P 2M 3m 4P 5P 6m 7m The vertical method proves to be more functional, as it keeps harmonic quality in mind. Memorize the sharp and flat order: Sharp order=F C G D A E B Flat order =B E A D G C F Notice that they are reversed! This makes things easier. Understand the note that is altered: All Major Scales alter up to the 7th note. All minor Scales alter up to the 4th note. E Major Scale alters: F C G D - raises them and makes them sharp till the 7th of the scale. Eb Major Scale alters: B E A - lowers them and makes them flat till the 4th of the scale. B Major Scale alters: F C G D A - raises them and makes them sharp. There are more tips, although relevant to other scales. Scales accidentals and flattened ones accidentals sum up to 7: E has four sharps, Eb has three flats. 4+3=7 G has one sharp, Gb has six flats. 1+6=7 C has zero sharp Cb has seven flats. 0+7=7