Piano Forum



International Piano Day 2024
Piano Day is an annual worldwide event that takes place on the 88th day of the year, which in 2024 is March 28. Established in 2015, it is now well known across the globe. Every year it provokes special concerts, onstage and online, as well as radio shows, podcasts, and playlists. Read more >>

Topic: Rhythm  (Read 2338 times)

Offline stillofthenight

  • PS Silver Member
  • Jr. Member
  • ***
  • Posts: 50
Rhythm
on: June 01, 2014, 10:06:03 AM


In 12/8 the simplest division of the dotted quarter beat unit is three eighth notes. Now technically that is 3 evenly spaced notes for each beat which is the same concept as eighth note triplets in 4/4 time (3 notes evenly spaced).

So I was trying to get a measure of 12/8 to sound like a measure of eighth note triplets in 4/4 and I had to set the 12/8 measure to where the bpm = 60 and in the 4/4 measure bpm = 40. I don't get why mathematically that works though? Why 60 and 40?

I know that this is going a bit overboard, but I like studying rhythm mathematically and seems I am able to better understand that way.

Offline mikeowski

  • PS Silver Member
  • Sr. Member
  • ***
  • Posts: 262
Re: Rhythm
Reply #1 on: June 01, 2014, 10:52:05 AM
In 12/8 time two eight notes = quarter note
In 4/4 time the triplet (so three eight notes) = quarter note
That's why beats that are counted in three have tempo indications either with eight = x or dotted quarter note = x, but never quarter note = x.

Offline nystul

  • PS Silver Member
  • Sr. Member
  • ***
  • Posts: 270
Re: Rhythm
Reply #2 on: June 01, 2014, 06:11:47 PM
Yes, the proper marking for the 12/8 measure should be dotted quarter = 40 bpm.  Since the dotted quarter is the actual beat of the music, that should be the basis for the tempo.  But instead it is marked quarter note = 60 bpm.  The length of a dotted quarter note is 1.5 times that of a quarter note.  40 x 1.5 = 60.

Offline lelle

  • PS Gold Member
  • Sr. Member
  • *****
  • Posts: 2210
Re: Rhythm
Reply #3 on: June 01, 2014, 09:04:44 PM
Yes, the proper marking for the 12/8 measure should be dotted quarter = 40 bpm.  Since the dotted quarter is the actual beat of the music, that should be the basis for the tempo.  But instead it is marked quarter note = 60 bpm.  The length of a dotted quarter note is 1.5 times that of a quarter note.  40 x 1.5 = 60.

I think you are right but I am not following your mathematical proof.

In both examples there are three notes per beat (in the first example three eighth notes, and in the second an eighth note triplet), and since they are played at the same speed, logically the first example has the pulse dotted quarter = 40 if the second example has quarter note = 40. What the bpm indication tells you is of course how many beats per minute you have. In the first example you have 40 dotted quarter note beats per minute. So one dotted quarter note beat is 1/40th of a minute long. With this information you can calculate how big fraction of a minute a "normal" quarter note would be:



So as a result you get that your quarter note will be 1/60th of a minute long, ergo there will be 60 quarter notes per minute, and your bpm in quarter notes becomes quarter note = 60.


Offline stillofthenight

  • PS Silver Member
  • Jr. Member
  • ***
  • Posts: 50
Re: Rhythm
Reply #4 on: June 02, 2014, 09:55:15 PM
Thanks lelle that seems it should clear it up, now I just need to internalize the math some more.

Offline timothy42b

  • PS Silver Member
  • Sr. Member
  • ***
  • Posts: 3414
Re: Rhythm
Reply #5 on: June 27, 2014, 06:05:04 PM
It's not apples to apples.

In one case it's dotted quarter that is the unit of beat, in the second it is the quarter.

So there is no way the metronome could be set the same.

If the quarter note has a measurement of 1, then 

40 *(1.5) = 60 * (1). 
Tim
For more information about this topic, click search below!
 

Logo light pianostreet.com - the website for classical pianists, piano teachers, students and piano music enthusiasts.

Subscribe for unlimited access

Sign up

Follow us

Piano Street Digicert