The two classical piano pieces Fur Elise and Tarantella before I played every note right at two recitals in front of a crowd. Mind you I'm a musicologist but not quite a musician though.
This post was edited by CosmicWunderkind at September 6, 2022 6:36 PM MDT
(I think that anyone who claims that he or she was great at it the very first time, or who claims to be great at it on every single occasion, is plainly and obviously lying.) ~
Playing a drum-roll properly. I took up the drums many years ago but have not played for nearly as long!
A roll is not as easy as it looks, to play as it should be, but one day it sort of fell into place.
I did not though pursue the snare-dumming tutorial, by Buddy Rich, to such arcanities as the 'Triple Flam Paradiddle'.
Ordinary Flams (equivalent to a grace-note) and Drags (with two grace-notes) yes. The basic Paradiddle (8 strokes so if marking quavers, fill a 4/4 time bar). Anything further.... no.
Actually the very advanced patterns would probably be lost on any listener not a skilled, experienced drummer anyway! To anyone else it would more likely just be a blizzard of quaver and grace-note strokes like a slightly lumpy roll; but the jazz and big-band drummers liked using such things to show how clever they were.
I still know these basic rhythm and fill building-blocks, called "rudiments", but I'd be well out or practice for playing them to a decent standard.
#####
Using a hacksaw and file properly - the former well enough to minimise having to use the latter!
====
Not really grinding practice but related to that...
Finally understanding some mathematical topics thanks not to mechanically following text-book examples and exercises, but to real-life applications throwing themselves on my mercy so they showed me at last what the numbers actually do to each other!