Rule #1: Never sneak into a song.
Rule #2: The notes are for those who don't know the tune.
Rule #3: Perfect pitch means nothing if you sing like a stick.
Many years back while in a band having five singers (Sharie and the Shades), our bass player, Ray, would remind us again and again to never sneak into a song. Step into that song exuding confidence and authority! Ray was our guru, having toured Eastern Canada in the 70's with the soft-rock lounge combo, The Lady and the Gentlemen. Ray was a seasoned performer, having had records released through RCA. He had the uncanny ability to play bass and rhythm guitar both by note or by ear, and was gifted with a set a jazzy pipes. Man, could that man sing!
It was also Ray who told us The notes are for those who don't know the tune. With a play list of over 400 songs in his head, Ray knew what he was talking about. In a philharmonic chorus, yes, each member ought to singing thee notes. Singing to scale and to time is essential for the overall sound of the choral group. Singing in a band is quite different. Even when doing covers, a singer need only be inspired by the original, not dictated by it. As long as the audience members recognize the song, you'll be fine.
After taking a few semesters of vocal training from a music conservatory and then going to busking school (joke), I have determined that Perfect pitch means nothing if you sing like a stick. This is the most pragmatic of my three suggested singing rules. Public performers who stand like a stick are signaling to the audience that another bathetic (not necessarily pathetic) performance is underway. Stick singers, not surprisingly, are incredibly commonplace. They are a dime a dozen and will likely earn a dime for every dozen passers by.
Here are more busking suggestions:
A busker ought to be much more than liminal. Buskers best be perceived as being wide awake and with it!
A busker ought to appear cordial to the crowd, and elastic to the song, sometimes tristful, sometimes jocund.
A busker (without instrument) ought to fillip. All the greats, from Dean Martin to Bobby Darin, Patti Page and our pet Juliette, filliped as they sang. Even Old Blue Eyes – the Chairman of the Board had his finger fashion snap when he crooned.
A busker has to scintillate to be successful. Figuratively, a busker ought to sparkle, providing the audience moments of brilliance.
And last, when it comes to song presentation … 'tis far better to be vinegar than to be vanilla!