Mikeonpiano, here are some general principles that I have learned and taught esp. to people coming from other instruments.
- The first principle is that any note can be played with any finger - there is no "position" as such, even if in beginner books it's taught that way for convenience.
- The keyboard has a regular layout of white and black keys, the latter being shorter, further back, and higher up. You have two hands which are mirror images, with short and long fingers, a thumb that is further back but a wide range of motion. You are also sitting centrally at an instrument that is larger than you where your bum stays in one place but you can pivot side to side, forward and back, circular, to reach places. Your arms have freedom of movement and can tilt your hand this way and that. These are your piano-playing realities. ---- The key layout, and the length of your fingers, will be two factors that work together. If you put your long middle fingers on the 3 black keys, and the shorter thumb and pinky dangling to the white keys, this should give you one picture.
- Your hand can cover a range of notes that might be an octave, or less, or a 10th if you have large flexible hands. There is a "territory" that your hand can cover. The notes in your music will stay in one "territory" for a while, and then in another territory. You sort of map out that territory for new positions of your hand. As a beginner it's probably too early to do this. A lot of material will have this written in - not every note, but "guide fingers. (1 under G (RH) tells you to move over so that your thumb is on G.)
- Your hands do not have to be "lined up" like parallel lines to the parallel lines of the keys - they can be angled any way, and constantly changing angles. If your notes are mostly black keys you'll be moving in to the fallboard, if mostly white, you're moving further out. It's like if you're reaching for different things, you'll move yourself closer and further away, and angle yourself, according to where things are. You should not be in a "piano position" where you are in a rigidly fixed place. You do want to stay balanced.
- Your hands can and should constantly change shape. Dr. Mortensen has some good videos on that. Do not lock your hand in "this group of notes" position.
- My teacher has students learn to use pedal very early, but also ensures that they learn how to use the pedal properly in its timing. Here the advantage is that you can learn not to tightly hold on a note for its whole duration, with your finger and hand possibly getting stiff. You can press and release a note and it will continue due to the pedal. You can get the habit of moving to the next note while the first one is still playing, being there ahead of time, relaxing your hand in between. Those reflexes may stay established for when you don't use the pedal.
Piano has some things in common with guitar. If you play a note on one string, (guitar), then another note on the next string, that first note will continue to sound unless you dampen it with your hand, or if you play another note on the same string. Piano also has that property of continuance. The dampers falling down are the hand that dampens the sound, but it is mechanically automatic. When you play a note and hold it down, you are simply holding up the dampers. On a digital, this is reproduced virtually, but not physically. Wind players and singers and violinists are used to having to keep producing the note's duration through continual effort. As a guitarist, you already have a feel for this property.
These are the things you are working with.
The piece you linked is played with pedal. I think I remember a whole note on the bass. That note will be struck but not held, so it's played like an eighth note but sounds like a whole note. when the pedal foot does its next up-down, it "erases" the whole note like a hand damping a vibrating guitar string. Freedom of movement, and moving along large spaces (pianos are huge compared to a guitar), are elements of this instrument.