I'm learning basic music theory, and I have a naive question:
Does a song with "100 quarter note beats per minute" have a pulse that is slower than one with "80 half note beats per minute"? Or they are incomparable?
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1It might help to read https://music.stackexchange.com/q/133783/78419 – Andy Bonner Feb 09 '24 at 20:32
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Consider a song written in half notes played at a tempo of quarter note = 100. That means you play 50 notes every minute. Now consider another song written in eighth notes played at quarter note = 100. That means 200 notes every minute, so it sounds four times faster even though the tempo is nominally the same. Beats per minute by itself doesn't tell you much. – phoog Feb 10 '24 at 00:27
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@phoog: Hi, it seems to me that your answer contradicts the answer of Aaron below... – InTheSearchForKnowledge Feb 10 '24 at 23:24
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It does. Aaron's answer is incomplete if not simply incorrect and I have downvoted it as a consequence. – phoog Feb 12 '24 at 15:31
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@phoog: Hi, thanks for your answers so far. I'm just confused about the relationship between tempo and the melody. Why we need the tempo while it doesn't tell us anything precise ? (in fact, it does tell us how many beats per minute, but given the fact that a beat can mean any note and a song can be written by using many many combination of notes which are not the same as the note taken to be the beat, so I see no precise relationship). Could you please help me with this question ? Many thanks. – InTheSearchForKnowledge Feb 12 '24 at 22:12
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1"Why do we need the tempo while it doesn't tell us anything precise?": It tells you something very precise, which is exactly how fast a given piece of music is. It's just that it's not the only factor determining the speed of a piece of music. The other factors are generally fixed for any single piece of music but can vary from one to the other, which means that tempo alone can't tell you which piece of music is faster. Consider: one car's engine is rotating 1600 times per minute and the other's 2000 times. Which car is going faster? It depends on the gear, the size of the tires, etc. – phoog Feb 13 '24 at 01:45
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"a beat can mean any note and a song can be written by using many many combination of notes which are not the same as the note taken to be the beat": The point of a metronome marking is to indicate tempo for a given song. You know what the notes are, so you can see how many of them to play for each tick of the metronome, or how many ticks of the metronome to hold one note. There is no universal measure of speed that allows you to say unambiguously that any given song is definitely slower or faster or the same speed as some other song. You are trying to use b.p.m. for an impossible task. – phoog Feb 13 '24 at 01:55
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First point to understand: any kind of note can be the beat. If you know about time signatures, you know that the bottom number could be a 4 (meaning a quarter note is a beat) or 2 (meaning a half note is a beat). It can get complicated (e.g. 6/8), but it's a starting point.
Next thing to understand: note durations don't tell you the tempo, from one piece to another. Say you've got these two pieces:
... and...
In each piece, you know the quarter notes are half as long as the half note. But you don't know whether a quarter note from the first piece is the same speed as a quarter note from the second. In fact, I could write the first piece in 4/2, like this:
... and it could actually sound just like the first example, as long as these half note beats are the same BPM as the first example's quarter note beats.
So what if the composer wants one piece to be faster? They could just write "fast," but how fast is fast, really? That's where metronome markings in BPM come in handy.
Third point: You don't have to set the metronome (or, for a conductor, wave the baton) to match the bottom number of the time signature. If one of the pieces above is meant to be very, very slow, like say if the quarter note in the first example is meant to be 40 bpm, it's hard to play along with a metronome that is clicking that infrequently. So I might just set the metronome to double that number, 80, and call it eighth notes, and give two clicks for every quarter note. So when you give a metronome marking for a piece, instead of just saying "it's 40," it's helpful to say what length of note that 40 represents.
Let's look at that "complicated" 6/8 that we set aside. If we have this:
... then a beginning understanding of time signature tells us that there should be six beats in the measure. But this is often actually how we write music that has two beats, but with three smaller notes in each beat (like triplets). If this piece goes very fast, the eighth notes might be much faster than we want a metronome or a conductor to do. The real "beat" would be three eighth notes long, or a dotted quarter note, and the metronome marking might look like:
Andy Bonner
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No. Beats per minute is literal: that is, 100 BPM is faster than 80 BPM, regardless how those beats are represented in notation. Whether those beats are represented as quarter notes or half notes is purely a notational issue.
Aaron
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... indeed, though peoples' perceptions of "speed" can certainly be influenced (rightly or not) by the number of quarter notes in a minute, since, we have to admit, that's a popular default for thinking about the "speed" of a piece. :) – paul garrett Feb 09 '24 at 20:16
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could you please tell me what is the purpose of specify what a beat worths ? for example 100 quarter notes beats per minute ? Many thanks!! – InTheSearchForKnowledge Feb 09 '24 at 20:19
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@InTheSearchForKnowledge I'm not sure I understand your question. Are you asking why BPM is specified for a piece? Why different note-types might be specified as representing the beat? Something else? – Aaron Feb 09 '24 at 21:07
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Ah, i mean that you have said that 100 BPM means that 100 beats per minute no matter what is a beat. So I wonder why should we specify that a beat worth (for example) a quarter note. Can you explain it to me ? Thanks! – InTheSearchForKnowledge Feb 09 '24 at 21:20
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@InTheSearchForKnowledge Try starting with what difference beat value makes in time signature and the various linked posts. – Aaron Feb 09 '24 at 21:37
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Hi, after a day of thinking, it seems to me that a song with more number of quarter note (in a given time, say 1 minute) is "faster" because we have to do it more quickly to be able to play more beats in the same amount of time. I think i'm wrong but don't know why it is wrong. could you please help me demistify it ? – InTheSearchForKnowledge Feb 11 '24 at 21:24
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@InTheSearchForKnowledge Music with more quarter-notes per minute is faster than a piece with fewer quarter notes per minute. Music with more beats per minute is faster than music with fewer beats per minutes. Quarter notes are notation; beats are an abstract idea. Beats can correspond to any kind of note. – Aaron Feb 11 '24 at 22:27
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@InTheSearchForKnowledge the metronome marking could be quarter=60 b.p.m. while the melody is written in eighth notes; then you are playing 120 notes per minute. Another piece could be marked half=80 with the melody written in half notes; this is 80 notes per minute so it will sound slower than the first piece even though it has more quarter notes per minute (160 instead of 60) and more beats per minute (80 instead of 60). There's also the question of harmonic rhythm, which has a significant impact on perception of speed. – phoog Feb 12 '24 at 16:23
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Does a song with "100 quarter note beats per minute" have a pulse that is slower than one with "80 half note beats per minute"?
Are you making a distinction between 'pulse' and 'beat'? If not, you've answered your own question. In the first, the 'beat' is a quarter note, in the second it's a half note. 100 beats per minute is faster than 80 beats per minute. Doesn't matter how you choose to notate the beats.
Laurence
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