The most common and most useful of these chords is the seventh, which you can use pretty much anywhere just to add a slightly different color to a chord, or in some types of progression to give the sequence of chords some extra thrust, because the added seventh is a mild dissonance, or clash, that makes the chord sound like it wants to move somewhere.
Chromatic alterations, such as sharps and flats, can be used to help create a more interesting chord progression in a piece of music. Ed Bell explains how to use these alterations effectively.
There are many ways in which a musician can turn their love of music into a side gig, and a great way to do this is to become a music teacher.
In this video, Josh Wright of joshwrightpiano.com explains both shifting and crossing, and the best way to use each when playing piano.
Another great way to create more interesting chord progressions is to use a pedal note or pedal point. A pedal note is a static bass note that sticks around for a few measures while the chords change over the top.
Energy in singing is equal to energy of air spinning through the vocal resonators and a too relaxed singer can easily misunderstand this very important aspect of vocal technique.