Questions & Answers about Я нажал не ту клавишу на пианино.
Russian has no articles, so it does not use separate words for a or the.
In Я нажал не ту клавишу на пианино, definiteness is understood from context, and ту helps a lot. Ту means that and here it strongly suggests the one I meant / the intended one. So English may use the wrong key, while Russian naturally says не ту клавишу.
Нажал is the perfective past tense of нажать, and it means a single completed action: the speaker pressed the key.
That fits this sentence well, because the idea is that one specific mistake happened: I pressed the wrong key.
Нажимал is imperfective and would suggest:
- a repeated action,
- an ongoing action,
- or focus on the process rather than the completed result.
So:
- Я нажал не ту клавишу = I pressed the wrong key.
- Я нажимал не ту клавишу would sound more like I was pressing the wrong key repeatedly / I kept pressing the wrong key / I was in the process of pressing it.