: Are 7th chords made up from 4 notes? I'm new to guitar, and I have been learning basic chords over the months. I know that C Major is made up from C E and G When learning C7, there's an extra finger and that makes up 4 notes,

Well, basically it's correct that the C Major chord is made up of the tones C, E and G. On a usual guitar, when you strum the "normal" C chord (not the barré one) and omit the low E string, the following tones sound: C E G C E. So that's five distinct tones ringing, but actually only 3 really different ones, yet in different octaves.

Your're right, the C7 chord requires the tone Bb to create a "minor seventh" chord (that's what the "7" means); the "minor seventh" tone is always 1 full tone below the octave above a base tone, so for the C tone, the "minor seventh" tone is the Bb above it.

When trying to play that on a guitar, the best choice is to put a finger on 3rd fret of the G string, so tone Bb rings. When you now strum, omitting the low E string, the following tones sound: C E Bb C E. As you see, there's no G in it. The G is the fifth (interval) tone above the C, and as others already commented, not so very important for the character of a chord (it makes it only more "bold" or "fat").
On a guitar, you always depend on how you can best put your fingers onto the neck.

Seventh chord and keys

Of course you won't usually see a C7 chord in a song which is in C major key, because there's no Bb "defined"; you will see it more likely in a song in key F major.

Dominant seventh chord

Some mentioned the "dominant seventh chord": the "dominant" is the 5th step of the scale; for C major, it is G. For F it is C, for G it is D. Together with the "sub-dominant", which is the fifth below the base tone, it forms the cadence: this is the sequence base chord (or tonic) - sub-dominant chord - dominant chord - base chord (tonic). For C major, it are the chords C - F - G - C, for F major, they are F - Bb - C - F. Play them and you'll notice that many songs use that scheme.

Now when you play C - F at the end, this sounds like a "real end", that's why this is called the "authentic end". If you play C7 - F, it sounds still more like that, but you still go from the dominant to the tonic. This is why the C7 chord is called the "dominant seventh chord" in that context.
(C7 - F sounds a little more beautiful than C - F, because it contains that tone Bb goes to tone A (the third tone of the F chord). This half tone step sounds lovley.)

Whereas a seventh chord virtually always "wants" to be "resolved" to the chord a fifth below, this needs not always be so. E.g. you may well use the chord sequence C7 - F7 - G7 - C7 to accopmany a song. Sounds cool.

The "above Bb" issue: inversions

Now to your last question, about starting the C7 from Bb. As i said, C7 consists of the tones C, E, G and Bb. Now, actually that's just the set of tones that may be used in the C7 chord. Now there's the concept of "chord inversion".
I explain it for the C chord first: it has tones C - E - G. In German we call that the "quint (=fifth) position", because the fifth tone above the C is "on top" of the chord.

First inversion: put the C one octave up --> tones E - G - C, "octave position".

Now the bass tone is the E, giving the so called "sixth chord". It's used as transition chord, the usual chord sequence is: C - C/E - F. The /E means "E in the bass, not the C".

Second inversion: put the E one octave up --> tones G - C - E, "third position".

Now the bass tone is G, giving the so called "quart-sixth chord". It's also used as a transition chord, the usual chord sequence is: C - C/G - G. The /G means (again) "G in the bass, not the C".

Doing inversion once more, i.e. putting the G one octave higher, we are back at the original sequence C - E - G (only one octave higher, but that's not of importance for that subject).

Inversions for C7

Now we can also do inversion with the C7 chord:

Base: C - E - G - B7

1st: E - G - B7 - C ("quint-sext-chord")

2nd: G - B7 - C - E ("third-quart-chord") (rather seldom used)

3rd: B7 - C - E - G ("second chord")

(the strange names in brackets stem from the "basso continuo" theory - do not worry about it, you would only need it for classic music: e.g. a chembalo accompaniment then very often only noted the bass tones and some numbers or symbols written above it, telling which chord to play above the given bass tone - everything else was free to the player's art)

Now i guess the 3rd inversion above is the one you are talking about when saying "above Bb". It's also used very often as transition chord; the usual sequence is: C - C/Bb - F(/A), to note here that the bass goes down a scale. You might want to add Fm/Ab - C/G - G to the sequence - very familiar i suppose (but hard to play on the guitar alone. In a band you would divide it up between guitar and bass).

But how to play that on a guitar? As i said above, you need to look how to arrange the fingers on the neck... For C/Bb, there's the following option:
do a barré on 1st fret, and do 2nd fret on D string and 3rd fret on G string. When strumming, omit both E strings. Now the tones Bb - E - Bb - C ring, making up a C/Bb. Although it's a little limited, and the Bb is doubled, it does the job. On a piano it were far easier - you just would go down 1 tone with the left hand.

Scales and intervals

There's no real need to learn scales or intervals before learning to play an instrument. But if you want to understand all the theory behind notes and scores, it's the very foundation! But i know a lot of (good!) musicians who can't even read notes and scores... Music lives from what you put into it as a performer, not from the theory :-D

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You can make all possible 7th chords that are consistent with harmonizing the diatonic scale by taking 4 consecutive 3rds of the major scale. The notes of the major scale are referenced by their degree (an index 1, 2, 3, 4, 5, 6, 7, 8 for Do, Re, Mi, Fa, Sol, La, Ti, Do). The tricky thing is that when we build chords we always use the major scale degrees as a reference with the chord root on 1. For example a minor chord is (1, b3, 5). The 3rd is flat because in the major scale the 3rd degree is a major 3rd. Flattening it makes it minor. So, a G Maj and G min chord are both built from the degrees of the G major scale. A variety of chords naturally occur in any key by starting on different notes of the key. For the triads we get the following pattern.

Maj occurs on 1, 4, and 5

min occurs on 2, 3, 6

dim occurs on 7

In the key of G maj you have G, C, and D major triads, and A, B, and E minor triads all in the same key. The formula for C maj is still (1, 3, 5) using the C major scale but in the Key of G it can be described as (4, 6, 8). It's like using absolute frames versus relative frames of reference in science and engineering. You can build a variety of 7th chords by adding another interval of a 3rd (more correctly the next note in the sequence of "every other note") to any of the triads (including Augmented, not provided).

You get the following basic 7th chords.

Major 7 = (1, 3, 5, 7)

minor 7 = (1, b3, 7, b7)

Dominant 7 = (1, 3, 5, b7)

Minor 7 b5 = (1, b3, b5, b7)

Full Diminished = (1, b3, b5, bb7)

You also have altered versions of these by moving one or more of the notes.

min Maj 7 = (1, b3, 5, 7)

Dom 7 +5 = (1, 3, #5 , b7)

etc.

The standard notation is that a "7" chord is a dominant seventh chord, hence the Bb.

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A "proper" C7 chord is C-E-G-B?. However, it is educational to look at what accordions, which have whole chords on a button do. While some older German accordions do the "correct" C-E-G-B?, this is more a quirk of history than anything else: most accordions use only three notes in order to have all chords have similar "weight" and air usage. On accordions with 4 chord rows, C7 is usually represented by C-E-B?, leaving off the fifth. If you really, really want the fifth, you can press the normal Cmajor key in addition and it will add the G.

On accordions with 3 chord rows, the "diminished chords" row is missing. However, C7 is represented as E-G-B? then and can also serve as Gdim (again with the fifth, namely D?, missing). Many chord accompaniment schemes alternate between a bass note and a chord, and if the chord does not repeat its root, that is surprisingly inconspicuous.

So functionally, not much more than the seventh (to establish the seventh character) and the third (to establish the major character) are really making a significant difference in character when absent.

The "weight" argument also applies reasonably well to piano accompaniments where an abundance of simultaneous bass notes tends to create a muddy sound character. Depending on the pitch there, it might be expedient to leave off the third (or only play it in a higher octave) since it has a higher "mud factor" than the fifth.

Guitars tend to suffer less from that affliction, so one usually is fine with sounding the regular major chord on all feasible strings and modify one of the higher strings to sound the seventh.

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Yes, seventh chords are made up using 4 notes. 1,3,5 and 7. That's why they are named 'seventh' chords. But that's going to be too simple! There are quite a few different 7th chords, and the one you're asking about is the dominant seventh.It's actually a chord that belongs to key F, rather than key C. The B♭ note that's added to the basic triad doesn't really belong to key C - which doesn't have B♭ in its scale.

You say it uses an extra finger - that's true here, but if you looked at A7, you can actually take a finger away, and play it with only two fingers, so don't think a 7th chord always needs an extra finger! However, from an open C chord, adding B♭ on 3rd string, 3rd fret produces C7.

A quick list of 7th chords - dominant; major; minor; m7♭5; dim7; mM7; aug7 covers most - each and every one featuring 4 notes. On guitar in particular, you can actually get away with playing only 3 notes - root(1), 3 and 7. Sometimes this is needed in order to finger it comfortably.

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7th chords are made of 4 notes, which is a sort of an extension of a typical triad making a chord. min7, M7, maj7, or 7 (a dominant chord which a C7 is an example of) are constructed with 4 notes.

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The chord you are describing is referred to as a dominant seventh, which flattens the seventh note of the scale. By doing this the chord becomes very useful for resolving back to the tonic of the scale because of the tension caused by the flatted seventh scale degree when it is combined with the other harmonies in the chord. Compare that to the major seventh chord (also a four note chord) where the seventh degree of the scale is not flattened.
The digital age brings easy access to a whole boat load of information about almost anything you may have a question about, but more often than not that information is incomplete and taken out of context. This usually leaves us with more questions than we had before we started asking. As long as you have questions, you'll need to keep searching for the correct answers. Personally, I don't expect to ever arrive at that point, but good luck searching.

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...Are 7th chords made up from 4 notes?

The simple answer is yes. C E G Bb is a dominant seventh chord and it has 4 tones.

In practice it is common to not play all chord tones - you can call those implied or incomplete chords - and sometimes the root of a chord is not actually play - implied or rootless chords.

A little more sophisticated answer is that chords are made from tones above a root. Those tones added above the root form intervals. So we can talk about chords as a collection of intervals above a root.

A seventh chord is minimally defined by a tone added a seventh above a root.

You could play only C Bb for a incomplete dominant seventh chord, or E Bb for an implied, rootless dominant seventh chord. The other chords used in the music will make more or less clear how such incomplete or implied chord are perceived.

...I saw in some website, that it's [C7] made up from "Bb"

Probably the intended meaning was something like: just a Bb alone above a root of C will provide an incomplete C7 chord. In that sense the C7 is "made up from" the addition of the "Bb." It seems like a poorly worded description.

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"I saw in some website, that it's made up from "B♭". Let's get that out of the way for a start! Yes, a B♭ does come into it, but that statement, as it stands, is nonsense. Carry on...

Yes, a major chord has three notes. If we consider the lowest note to be the root of a major scale (yes, if you want to understand theory you'll need to know about scales) it's the 1st, 3rd and 5th notes of the scale. C major chord is the 1st, 3rd and 5th notes of a C major scale - that's C, E and G.

So a 'seventh' chord should be the 1st, 3rd, 5th and 7th notes of the scale, right? C, E, G and B? Sorry, no! That's a 'major 7th' chord, written C(maj7). 'C seventh', written C7, is C, E, G, B♭. The basic C chord plus the flattened seventh.

You want some 'why'? Because this type of chord first appeared as a 'dominant 7th'. An addition to the dominant chord, the one built on the 5th note of a scale. That's the 5th, 7th, 2nd and 4th (it wraps round) notes of the scale. And this chord type is often called a 'dominant 7th'. The 'dominant 7th' in the key of C is G7 - G, B, D and F. Whereas C7 - that's C, E, G, B? - is the 'dominant 7th' of F major.

Now, you have the opportunity to avoid falling into a very common misconception.

Indeed, C7 can be a gateway from the key of C major to F major. Something 'borrowed' from F major, that takes us into F major. But it can also be firmly 'in C major'. One example, which I'm sure every novice guitarist will have already encountered, is the 12-bar Blues. One of these in the key of C will use three chords, C7, F7 and G7. Your melodies will doubtless include lots of flattened 3rds and 5ths (E♭ and G♭). And all ABSOLUTELY IN C MAJOR. Notes that aren't in the scale are OK, and don't necessarily imply a change of key.

Get this idea clear at the start, and you'll avoid a lot of brain-ache when you encounter other 'not in the scale' chords!

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A dominate 7th chord (often written as x7 where x is the root) will contain the Root (1st degree), 3rd, 5th, and flat 7th.

Therefor a C7 will be C, E, G and Bb.

At times a player can choose to leave out a note, usually the 5th or the root but in those case it is common that the other players will be playing them or that they are implied. The 3rd and 7th are a little more important because if you don’t play them it is harder to tell if it is a major or minor 3rd or a major or minor 7th.

As far as what you found on the internet that it will be “made up from Bb”...I am not sure what that means but don’t believe everything you read on the internet.

EDITING TO EXPAND ON THIS:

If you look at the major scale and build chords off it every key will have the same quality of chords built off the same scale degrees.
For example the chord build off the tonic (root) of the key will have a Major triad or a Major 7th chord built off it.

For the key of C the I chord (one chord) is C E G or C E G B and for the key of G it is G B D (G B D F#). If you looked at the distance between those notes (i.e. the intervals they are the same for each, because all major scales will have the same intervals between notes.

You can do this from other scale degrees too. If you start at the second scale degree you get a Minor triad or a Minor 7th chord.
In C the second scale degree is D, so the Diatonic chords (the chord that belong to the key of c for that scale degree) are D F A and D F A C. Notice that the F is natural, because that is the note that is diatonic to the key of C and the F is natural as well for the same reason.

If we want to build a major triad or a major 7th from D you would need to use the notes that are diatonic to D as we have already seen that a chord built off the root of the key is a Major triad or a Major 7th: D F# A or D F# A C#.

So, where does this Dominate 7th come from? glad you asked. It comes from the 5th degree. Look at the 5th degree in C. It is G. If we build a chord from G using the notes from our C scale we have G B D, a major triad. So, a G major triad is diatonic to C. It is also Diatonic to G (as we saw above) but serves a different function as it is built on a different scale degree. If we turn this into a dominant 7th chord we get G B D and F. Note that it is not F# which would be diatonic to G but F natural which is diatonic to C.

So, the 5th scale degree is a diatonic 7th chord. Now, back to your question...How can we build a C7? Well, what key does C function as the 5th degree of? F Major! So, if we take the key F we have F G A B♭ C D E and F. If we take those notes and build a chord starting on C we get C E G and B♭!

If you want to build out all the chords in a major key we would have:

Triads:

Major : I
minor : ii
minor : iii
Major : IV
Major : V
minor : vi
diminished : Vii°

and 7ths:

Major 7th : I Maj7
minor 7th : ii min7
minor 7th : iii min7
Major 7th : IV Maj7
Dominant 7th : V7
minor 7th : vi min7
minor7thFlat5 : Viimin7♭5

One thing to note is the way the chords are named:

Major7th chord is a major triad with a Major 7th (interval about the root of the chord).
minor7th chord is a minor triad with a minor 7th.
7th (Dominant 7th) is a major triad with a minor 7th.
Minor7th flat5 is a Diminish triad (root, minor 3rd, diminished 5th) with a minor 7th.

(Notice that in the above definitions the triad qualities mentioned match the triads that are diatonic to the key, which makes sense if you think about it)

There are other 7th qualities that are not diatonic to a major key, such as MinorMajor7th, but lets not get ahead of ourselves.

Just because a chord is not diatonic to the key doesn't mean you can't use it, and actually non-diatonic chords (or borrowed chords, or secondary chords) are used all the time in all styles of music.

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