Kaan

There is a playing reason as well, which is easy to appreciate once you have needed it.

The key block sets the space around the outermost keys. Without it — with the case wall coming straight down beside the lowest key — your hand hits the side of the instrument when you play the bottom of the keyboard with any force or with the hand angled. On a piece that lives down there, that matters.

The height of the blocks is also part of the geometry. They are typically level with or slightly above the white keys, so they do not obstruct the hand travelling along the keyboard, and on many instruments the upper surface is where the fallboard rests when closed.

So: structural first, ergonomic second, and it is doing both jobs at once.

The historical context is worth knowing because it undercuts the "natural versus artificial" framing that the claim rests on.

Before standardisation, pitch varied enormously — by place, by period, by instrument type. Surviving organs and wind instruments span a range of well over a semitone. There was no single traditional pitch that 440 replaced; there was chaos, and orchestras had been drifting steadily upward for a long time because higher pitch sounds brighter and more brilliant.

The standard was agreed in the twentieth century precisely so that instruments and recordings could work together. Choosing 440 was a practical decision about a convention, not a departure from a natural order.

Which means the claim has the history backwards: there was no lost standard, only an absence of one.

Your diagnosis is right and it points at the fix. The problem is not the difficult bar — you can play that. The problem is the junction, and you have never practised the junction as its own thing.

The technique is sometimes called building a bridge, and it is the single most useful practice method there is:

1. Take the last note or two of the earlier bar and the first note or two of the later bar. Nothing else. Two or three notes total.
2. Play just that fragment, very slowly, until it is completely secure.
3. Extend backwards by one note. Secure it.
4. Extend forwards by one note. Secure it.
5. Keep growing outward until the fragment covers both bars and joins the surrounding music.

The key insight is that you are practising the transition itself as a unit, rather than practising two things you already know and hoping the join looks after itself. That join is where the actual difficulty lives and it has never had any attention.

There is a second technique that guitarists use, and the two are often confused because they look different but sound related.

Longitudinal vibrato — the rolling motion along the string, as you described. Modulates tension, gives a gentle vibrato, and is the classical guitar approach.

Lateral vibrato — bending the string sideways across the fingerboard, repeatedly and slightly. This changes tension much more dramatically and is the electric and steel-string approach. It produces a wider, more obvious effect and it only goes sharp, never flat, because you can only add tension.

That asymmetry is worth noting: on a violin, vibrato oscillates around the pitch in both directions. On a guitar it mostly pushes sharp from the fretted note. Good players compensate by aiming slightly under the pitch so the average lands right, which is a genuinely subtle piece of technique.

The place to look for practical experience with this is congregational singing, where people have thought hard about it for a long time and where the goal is exactly yours: get a room of non-singers to participate.

The consensus there is close to what has been said — keep the melody within about an octave, top out around C or D above middle C, and be more willing to go low than high. A note that is slightly too low is mumbled; a note that is too high is not attempted.

The other piece of advice from that world is worth passing on: the highest note matters far more than the average. A tune that sits comfortably and reaches up once for a single note will still lose people at that note, and they often do not rejoin. When choosing a key, find the highest note and set the key from that, not from where the melody generally sits.