Originally Posted by: Whune

I've had experienced players tell me that add9 2nd... it doesn't matter... that it's the same scale degree

[br]but to me octave difference matters

[/quote]

Yes, it's important to the actual sound of the voicing. And, yes, you are right that the 9th is a 2nd an octave higher. This is the case in most piano & orchestral music (which is where these voicing designation originated). But that's because you've got a lot more real estate to fill. Often voicing those chords on the guitar is tricky, so they are sometimes regarded as interchangable.

For example, a Dsus2 chord is 1st (D), 2nd (E), 5th (A).

|----------------------------------|

|----------------------------------|

|-----2----------------------------|

|-----2----------------------------|

|-----5----------------------------|

|----------------------------------|

That's hard to play on a guitar. So, it's acceptable to voice the E an octave higher & call this a Dsus2 chord.

|----------------------------------|

|-----5----------------------------|

|-----7----------------------------|

|-----7----------------------------|

|-----5----------------------------|

|----------------------------------|

In the end, that's what music notation is for. You can precisely specify which octave you want a note in.

[quote=Whune]

why's it called sustained?

The sus means suspended.

https://en.wikipedia.org/wiki/Nonchord_tone#Suspension

The name came from the contrapunctal technique of "suspending" or temporarily delaying the arrival of a note while moving from one chord to the next. In the case of the sus4, the 4th to the major or minor 3rd.[br][br]The suspended note is a chord tone held over or "suspended" from the previous chord, leaving you hanging waiting for the arrival of the major or minor third to give a resolution. The classic, timeless example is any Bach chorale in which he uses the candential I 6-4 chord or the V7 chord or even the I at the end of a line in a suspended form, then follows with the third. Example with a V7 4-3 - I cadence, the F from the G7 moves to E eventually, but not right away. At first the F still sounds when the other voices have moved to the C chord.

|--------------------------------------------|

|-----6--held--6 resolved--5----------|

|-----4-->>>--5--------------------------|

|-----5-->>>--5--------------------------|

|-----5-->>>--3--------------------------|

|--------------------------------------------|

G7 >>> Csus4 >>> C

So, the term originally indicated a type of functional motion. However, in modern music it's not necessary to have that motion, you can simply use the chord voicing ornamentally because you like the sound of it.

Examples abound in pop and rock guitar, the Beatles tune "I Need You", main riff in Van Halen's "Unchained".