The last rule to follow is: to listen and experiment.
This, of course, applies whether we are talking about 7th chords or anything else related to arranging music – if it sounds good, it is good.
Don't be afraid to try!
Are you playing a song with many verses? Try to apply one of my 7 tips to each verse. Play every other version as written in the notes, and play according to the tips from Chapter 4 (using only 7ths) on the other verses. Or do something completely different! The worst that can happen is that it doesn't sound good.
One can also, beneficially, observe how others think and act. Compare different songs with each other, see how one and the same song is arranged in different songbooks. This can generate many new ideas for your own playing.
A little rule of thumb can be good to keep in mind: If there are several of you playing together, play from the same sheet music/version/arrangement of the song. That way, you avoid confusion and it will sound much better!
Because it doesn't help if everyone chooses to, for example, play a G7 as a G if one instrument in the group doesn't. It is sufficient for one instrument among all to play a seventh for it to become the sum of what the whole band plays.
However, the reverse is not true. If everyone plays a seventh chord except one in the band, the sum of the music becomes a seventh chord. It doesn't matter if the band plays a G7 and one single person in the band, however determined and persistent, plays a G – it will still sound like a G7.
Good luck!
