A Gm7 may be the same notes as Bb6, so it won’t scream discord, but in most cases the bass note is important in the overall musical feel of a chord progression. So using just a Bb without the 6th might actually sound better than the alternative with note G as the bass. You have to judge.
These additional chord notes make a great difference in some playing. For example piano players use both hands and how they add the additional notes can make the playing so much more professional. Good players will be using 6ths, 9ths, flattened 5ths etc all the time and sound amazing. But on arranger auto accompaniment sometimes the difference is hardly noticeable - especially if the chord is held for only a beat or two.
So is it really worth the effort of technical correctness in concocting a difficult lh position? You have to listen and decide. Bear in mind that the extra difficulty for the lh may mean you don’t play that passage as smoothly or as well, so the questionable gain of playing the technically correct chord is sometimes more than offset.
Another thing to watch for is sometimes the chord additions are just recognizing that the 6th appears in the melody, so it’s not important to add it to the chord.
Overall, the important thing is that the object of playing music is to sound good, not to be technically correct.
Mike
