theory advice

[greybeard]

does it matter what octives of the notes are used? like, does the C have to be the bass note?

Because you have designated the chord as xx/C, you are specifying that the C is the bass note.

i guess it would because C is the 5th of F. it's funny but i think if it was written as C/F7 i would have had a better idea of how to play it.

The convention is chord/bass note. Your definition would be understood to be a C chord with an "F7" bass note. You can't define a bass note of F7.
An F7 consists of F, A, C, Eb, so you could have any of those notes (other than F) as a bass note (F7/A, F7/C, F7/Eb). Obviously, if F is the bass note, it's not a slash chord.

[Misanthrope]

Is it a convention that the chord should be written as if it includes the bass note? I'd always thought it left it out as you're specifying the bass note anyway... ie, if I were to add the seventh to F as a bass note, I'd write F/Eb rather than F7/Eb.

[hbriem]

Well, F7/C means "F7 chord over C bass note", so yes, the C has to be the bass note. Although usually the bass player would play the C.

C is the 5th, so this is known as a 2nd inversion chord. If the 3rd, A, were the bass note (F7/A), it would be known as a 1st inversion chord. F7 is a four note chord, so it could theoretically have a 3rd inversion (F7/Eb).

Such chords are often colloquially called "slash" ( / ) chords.

but i think if it was written as C/F7 i would have had a better idea of how to play it.

But that would make no sense. C chord over F7 bass?

[greybeard]

Is it a convention that the chord should be written as if it includes the bass note? I'd always thought it left it out as you're specifying the bass note anyway... ie, if I were to add the seventh to F as a bass note, I'd write F/Eb rather than F7/Eb.

Writing the chord and specifying an "out-of-chord" bass note is a hybrid chord. Then you're getting into chords where the bass note also becomes the root - not something I've any real experience with, as yet.
As helgi say, a normal slash chord is an inversion.

[NoteBoat]

There are really two types of slash chords, just one way of writing them...

When the note after a slash is contained within the chord, it's an "inversion". F/C shows you the fifth has to be the bass note - that's "second inversion" in theory. If you were using a different inversion notation, it would be shown a different way - in higher-level theory books it's typical to use 'figured bass', which would show the chord as F64 (the 64 would be written above/below each other, like a fraction)

If the note after the slash isn't in the chord, it's technically a non-harmonic tone that happens to occur in the bass voice. Greybeard calls it a 'hybrid chord', which is probably an apt description - in the sense that guitarists like 'chord' to equal 'fingering'

Let's say the bass line of that F/C chord was going to move down chromatically to an A (C-B-Bb-A), and when it gets there, the chord changes to Am. You could write that as:

F/C -> F/B -> F/Bb -> Am

The F/B and F/Bb aren't really chords - or rather, they aren't F major chords. You could turn them into chord names, using F(+11) and F/11, but that doesn't give you any harmonic information... the harmony is F throughout. In any theory book, that would just be written as an F chord, and the authors would figure you'd know enough to see they're not chord tones.

[improvgtrplyr]

ok...i got the idea from other posts that it's bass note/chord. not chord/bass note.

simple enough: F7/C = chord (F7) / bass note (C)

thanks for the input

[improvgtrplyr]

i found out what these chords are called.

a lesson in guitar player mag calls these chords "polychords"

(i edited out the quote from the mag...not sure about legal issues)

[hbriem]

No, polychords, at least as the term is commonly used, are more complicated than slash chords.

A polychord is when two chords are played at the same time, not just a chord and a bass note. In order for the ear to hear them as distinct chords and not just a chord with many notes, the chords need to be separated in either registre (different octaves) or timbre (different instruments) or both.

13th chords, which contain 6 different notes (1-3-5-b7-9-13) may be thought of as polychords. They typically serve a dominant function.

[NoteBoat]

That's a really confusing topic - because polychords are written the same way as slash chords.

In polychord arrangements, the idea is either:

1. Create harmonies that are more complex than you can do on a single guitar, or

2. Explore bitonality

The complex harmony idea is the easiest to grasp. A full C13 chord has seven notes - so you can't play it on one guitar; you have to simplify the voicing. But if you split the notes into two groups, C-E-G-Bb and D-F-A, you have all seven tones. So if one guitar plays C7 and a second guitar plays Am (or Bbmaj7, or any other 'overlapping' set of tones) the listener will hear a full C13.

Bitonality is a composition written in two keys. They tend to be more experimental, even though they've been around for about 100 years.

The only real clue you have to determining whether you're dealing with polychords or 'slash' chords is the placement of suffixes (unless you read music, in which case you could tell from the score). If a tune has C/E, Am/G, D/B7 - you have polychords. You can tell because full chords (Am, B7) appear both before and after the slash.

Of course, given the quality of notation on the internet... polychord symbols might just be slash chords too, with some chord names in the wrong places!

[improvgtrplyr]

the Nov. '95 issue page 132 of GP says that is polytonality (playing two different keys).

but adding a diatonic or a non-diatonic bass note to a triad makes it a polychord.