Difference between 3/4 and 6/8 Time Signatures,

[YammyFan]

 I think  that "Skye Boat Song " is usually played in 3/4. But some sheet music calls for  6/8. I'm wondering why  some players prefer  6/8.

[jes826]

Basically, the difference is only in the notation of the music.  Here are two YouTube links that will demonstrate the different notation although the end product can be the same song.

John

3/4 version - https://www.youtube.com/watch?v=0Xjs6wYUnuQ

6/8 version - https://www.youtube.com/watch?v=iGEnA-gKhjI

[mikf]

As John states above, music was historically arranged into 'bars' with a time signature to make it easier to write/read. It doesn't change the actual notes. however, convention means that it can provide clues to the musician as to the style/rhythmic feel the composer or arranger intended, especially with the addition of a few words eg 6/8 jig time, or 12/8 doo wop.
In this particular piece it makes little difference, although there is a possible subtle point, because  6/8 actually has more in common with 2/4 than 3/4, being 2 beats to the bar with a triplet on each beat, whereas 3/4 has 3 beats to the bar.
There has been much discussion on this forum about the fact that Yamaha shows 6/8 and 12/8 styles as being 4/4 - is this technically correct? But it has little relevance because the rhythmic feel of the music is already defined by the style /accompaniment anyway.
Mike

[Robert van Weersch]

But it has little relevance because the rhythmic feel of the music is already defined by the style /accompaniment anyway.

Well, if you want to play something like "Nothing Else Matters", then then you'll get out of sync with the accompaniment because it works in bars of 4 beats, but sometime you'll need to play 2 bars. On a T5, this is a problem. On a Genos or SX900 you can 'reset' the style while playing. I solved this by using a tool from one of the forum members, which allows you to create a break which runs on double time, with all the notes doubled in length, so effectively, the break then does a 2/4 in stead of 4/4.

[mikf]

Robert, you are correct, there are some songs where total accuracy might demand a different approach. But it's not a problem more than 99% of the time.
Arrangers are machines and cannot do absolutely everything that people can do, at least not without some tweaking. But it's also true for most musical instruments, they all have limitations that the player works around best he can - try playing dimished chords on bagpipes or even producing all the notes of many songs. 
You typically have a choice of going to some technical shenanigans to find an exact solution, or just tweaking the song to fit. The song Memory from Cats is a great example, it has the one bar change of time signature which is a pest on an arranger. There are technical ways to handle it, but involve more effort than I think it's worth, so I just stretch the bar and no-one even notices.

Mike