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I don't know if it is possible to calculate BPM with timing and length only? For example, I have the timing of each note, that is the first note starts with 0s, second note starts with 2.1, the third note starts with 3.... Then, can I calculate BPM without measures and time signatures? Thanks.

Megan
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  • BPM is directly related to timing - and vice versa, but the question needs more clarity, please. – Tim Aug 30 '22 at 07:33
  • Then how to calculate? Okay, I will edit it – Megan Aug 30 '22 at 08:16
  • @Tim I edited it. Hope it helps – Megan Aug 30 '22 at 08:18
  • This post should help: How to figure out the length (time in ms) of a bar from bpm and time signature? – Elements In Space Aug 30 '22 at 08:21
  • @ElementsinSpace Hi, thanks for providing the info. I saw a formula in that post written about "BPM" = "beats" / "time in minutes". What does beats in this formula mean? – Megan Aug 30 '22 at 08:24
  • For example, if you have a bar of of music in the time signature 3/4, there will be 3 beats in each measure. – Elements In Space Aug 30 '22 at 08:27
  • @ElementsinSpace But how if I don't have time signatures? I only have timing and duration of each signal – Megan Aug 30 '22 at 08:31
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    ... but as you don't have measures or time signatures, are "beats" the moments that you would tap your foot. – Elements In Space Aug 30 '22 at 08:31
  • @ElementsinSpace haha, well, because my data is an array, not an audio. So I can't listen to it – Megan Aug 30 '22 at 08:33
  • If the times were 0, 2, and 3 seconds exactly, a beat would probably be 1 second long, (because each note would fit nicely on a 1 second grid). But 2.1 is an odd number. – Elements In Space Aug 30 '22 at 08:40
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    The real question seems to be "what constitutes a musical beat in my data". And then you would have to explain what your data is. If you want to calculate Things Per Minute, you will have to know what a Thing is, and what a Minute is. I guess you know what minute means, so that leaves finding out what a beat is. – piiperi Reinstate Monica Aug 30 '22 at 09:09
  • I recall 2 other transcribers and I transcribing the same particular video game cutscene theme, but one of the transcribers and I agreed that the tempos used were quarter note = 70 bpm into quarter note = 62 bpm (not quite sure how fishy the agreement is since I published my transcription first), but the other transcriber used quarter note = 140 bpm into roughly quarter note = 128 bpm, then doubled the note lengths accordingly. ...This might be enough to say that the answer is no, actually. – Dekkadeci Aug 30 '22 at 17:39
  • @ElementsinSpace 2.1 seconds is 7/200ths of a minute, and (3 - 2.1) seconds is 0.9 seconds, which is 3/200ths of a minute, so there is actually a standard metronome setting common to both durations. However, a 7-pulse note is normally only followed by a single-pulse note (double-dotted rhythm), so if these measurements are correct there is probably some rubato or other tempo change going on. – phoog Aug 30 '22 at 18:22

2 Answers2

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This problem can be solved only by making some additional assumptions. For example, you might find that all the notes line up with a multiple of 0.3 seconds, as in the example given here. But you have no way of knowing if a note lasting 0.3 seconds is a quarter note at 200 quarter notes per minute, an eighth note at 100 quarter notes per minute, or a sixteenth note at 50 quarter notes per minute, among many other possibilities.

Furthermore, it's possible for notes with the same notated value to have different durations because the tempo can change over the course of a piece. It might accelerate or decelerate either permanently or temporarily, or there might be some notes played "out of time" with indeterminate duration. This might explain the odd 7-to-3 ratio of the durations cited in the question.

phoog
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  • I've now seen multiple examples of transcribers, including me, notating transcriptions of the same music with different BPM...and corresponding different note lengths. I mentioned an example I was involved in as a comment on the question, but another one I've seen lately is one transcriber notate the bulk of a boss theme as quarter note = 120 bpm and another transcriber notate that same bulk of the same boss theme as quarter note = 240 bpm and double the note lengths accordingly (but keep the same meter). – Dekkadeci Aug 30 '22 at 17:49
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It's BEATS per minute, not NOTES per minute. Even if all the notes are the same length, they may not each add up to a full beat. And the grouping of notes into beats can be arbitrary.

So, without much more information, I think your answer is 'No'.

Laurence
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