I'm trying to learn music theory but I have problems understanding beats. I understand that the time signature decides how many beats there are in a bar and that some of these beats are stronger and some are weaker but I don't get what that means in practice.

Is the beat just something that is there to help the composer structure the music? Like for instance placing long notes on strong beats...

Or is it something that the instrument players should think about? Should a piano player hit the key with more force or with a different timing when playing a note that starts on a beat?

I'm trying to learn music theory but I have problems understanding beats. I understand that the time signature decides how many beats there are in a bar and that some of these beats are stronger and some are weaker but I don't get what that means in practice.

Perhaps listening/studying to famous pieces done with different time signatures and rhythms would help?

Is the beat just something that is there to help the composer structure the music? Like for instance placing long notes on strong beats...
Or is it something that the instrument players should think about? Should a piano player hit the key with more force or with a different timing when playing a note that starts on a beat?

Yes.

Composers use rhythm/beat to help structure a piece of music and the performers use rhythm/beat to help know how to perform the piece. For example I'd play an upbeat note differently than I would a note landing on a downbeat. Especially a strong downbeat (depending on the time signature). But the timing placement of a note (which is what rhythm/beat is) isn't the only thing to determine how strongly a note should (or shouldn't) be played. Melodic motion (upwards, static or downward) as well as harmonic (chord) changes really play a factor as well.

Another thought - you can create a melody and by only changing the rhythm of that melody later in the piece create something that feels a bit different. More fresh.

Edit: What I'd recommend doing is studying multiple performers of the same piece to see how different players interpret the music differently. Do this while also studying that piece of music as well. Theme and variations are also very useful for seeing how the same melody can be changed and twisted to sound quite different. Think of Mozart's theme and variations on Twinkle Twinkle Little Star:

And here's a student's theme and variations - I'm sharing it because the video is easier to "see" the notes.

Thank you, I appreciate the help. I think my understanding is a bit better now, but please tell me, the first video sounds better (more beautiful) than the second one, is that because the first video is played by a real musician that takes the beat/rhythm into account when playing the notes while the second video is a computer program that simply plays the notes as-is?

please tell me, the first video sounds better (more beautiful) than the second one, is that because the first video is played by a real musician that takes the beat/rhythm into account when playing the notes while the second video is a computer program that simply plays the notes as-is?

The first video sounds better because:

1) it's a real person playing...

2) ... on a real instrument instead of a virtual one...

3)... and it's piece is composed/arranged by Mozart, generally considered one of the greatest composers of all time.

Whereas the second one is a student's work. Not knocking it but most of us cannot hold a candle to Mozart.

:)

i'm more familiar with nonwestern notation eg. the tal system, which is a system of emphatic beats. i don't think there's really a hallmark for "understanding" them because rhythmic sensibilities are an expression of style.

i will throw out a thought on tempo.. style depends on tempo, eg. placing hits 1/16th off the beat sounds syncopated at certain tempos but a mess at others... i have this idea that we should generally think of tempo as related to heart rate.

I'm trying to learn music theory but I have problems understanding beats. I understand that the time signature decides how many beats there are in a bar and that some of these beats are stronger and some are weaker but I don't get what that means in practice.

Is the beat just something that is there to help the composer structure the music? Like for instance placing long notes on strong beats...

Or is it something that the instrument players should think about? Should a piano player hit the key with more force or with a different timing when playing a note that starts on a beat?

The time signature provides an outline of the rhythmic pulse of the song. There are no hard and fast rules about which notes should be emphasized. The main piano part from Benny and the Jets by Elton John emphasizes each of the quarter notes of a 4/4 pulse (or, as you were referring to them, the strong beats). In contrast, the guitar part from La Grange by ZZ Top emphasizes the off-beats of each quarter note of a swung 4/4 pulse (or, as you might refer to them, the weak beats). Both of these parts create a strong effect in the context of their respective songs. The time signature is just a framework to be decorated in creative ways in order to emphasize a certain feel.

The time signature is just a framework to be decorated in creative ways in order to emphasize a certain feel.

And some composers intentionally write rhythms/phrases "over the measure line" to blur or create a fusion of multiple time signatures, either for an entire song or just chunks of it.