time signature denominator

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drmoore
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Hi,

I am struggling with time signature denominators. If I use denominators other than 4 (ie (7/8 9/8 13/8) this does not seem to make any difference to the click or to any of the bar snap tools (they seem to calculate as 7/4 9/4 13/4). Or am I doing something wrong here?

Any help much appreciated.

Dave

paul
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ardour's conception of bar|beat time is slightly different from other DAWs and will likely change in the future. meter is handled in the standard way: a meter of 7/8 is taken to mean 7 beats, each 1/8 note in length. however, the tempo specifies how many of the denominator note lengths there are per minute *NOT* how many 1/4 notes there are per minute. thus, if you change only the meter, and leave the tempo at, say, 120bpm, you end up with the same click rate - it used to be 120 1/4 notes per minute, now its 120 1/8th notes per minute. thats because ardour is interpreting the "b" in bpm to mean "beat" and not quarter/crotchet.

as i mentioned, we may modify this in a future version. i still consider the standard handling of this to be wrong, but it does have the force of convention standing behind it.

drmoore
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Thanks for your reply paul. Just found issue 0000940 which addresses the same point. I take your point about the tempo change and will use this as a work around. However, I would say the standard (other DAWS) handling of this is correct (ie you would have a meter notation on a score quarter note/crotchet = 120bmp) and a signature of 7/8. I think you will find a lot of musicians would be confused here. I would be happy to have a look at this, do you think it could be a simple change? (ie not too deeply ingrained in many parts of the program)

Another possibility might be to have a dropdown in the edit tempo that lets you select a denomination at which the bpm relates. Or simply the text for "Beats per minute" could read from the current signature and display Crotchets per minute, Quavers per minute which would be clearer in my mind.

Seb
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I know lots of people are into your "even beats" but what if the bar doesn't go in integer crochets? 3/8 annyone, or ? I for one think you should stand with your convictions and defy the "force of convention" if it's wrong, Paul!

drmoore
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Sorry I'm not sure where you got the term "even beats" from?

A meter marking of crochet = 120bpm means that a note length of one crotchet should be played such that 120 of them would fit in a minute i.e. a crotchet is 1/2 a second duration. If I was following a score in 4/4 which changed to 3/8 but showed no change in tempo I would still expect a crotchet written in either of the bars to last the same absolute duration (1/2 second). In ardour it would be twice as long in the 3/8 bar hence the need for the tempo change. While this can be worked around it does mean inputting tempo changes for every signature change (if there is a change in signature denominator) which seems unnecessary to me. Are we talking about convention of a few DAW applications or that of common musical notation?

Pankot
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Just posting to agree with drmoore - In a piece which has measures of both 4/4 and 7/8, for example, the bpm would always refer to the crotchet. Well, to be more precise one would specify "crotchet = 120bpm" or what have you.

Probably the best solution is to allow the pulse to be specified *either* in beats per minute (current implementation) or crotchets per minute via an option. The current implementation - which is simpler and fine for the majority of projects - can stay default, and the other option allows projects which use complex mixtures of time signatures to be handled naturally.

thorwil
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And here I thought all the time that the B in BPM stands for Beat and basta! It most certainly doesn't stand for Crotchet :)

tgoose
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I don't believe "BPM" has ever been a standardised (or even musically "correct") notion.

Ardour's handling of metronome marks (if I'm reading this correctly - I don't use clicks/bars when I'm recording and I'm not at home to look!) is more in line with musical notation as it has been for the last several centuries.

mm. 100 in 4/4 means 100 crotchets in a minute
mm. 100 in 7/8 means 100 quavers a minute

If that's how Ardour handles it then I support it entirely - otherwise you need to use two different counting systems at the same time! As Pankot says, maybe an option in the preferences would sort this out for both sides :)

Seb
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> .. the term “even beats” ..

i meant even metres, like 4/4.

and yes, the situation you describe is maybe inconvenient but i can't see how you can have a 3/8 metre with a metronome if the metronome is hardcoded to click on crotchets.

drmoore
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I don't completely agree with tgoose here because a change of time signature would not always be accompanied by a scored change of tempo. So if you have a tempo mark of crotchet=100 (3/4 signature)at the top of a score and the time signature changes to an (3/8) during the piece but we don't see another tempo mark then I would expect a notated crotchet to last the same amount of time.

If we had a different situation where the piece started in a time signature with 8 in the denominator then would we not see a tempo mark like quaver=100.

In my opinion it would make sense to always specify the tempo mark in association with a note length. So the ardour tempo dialog could be modified to include an entry field for the note length that the tempo 'beats' relates to. This field could be defaulted to the denominator of the last time signature in the session.

I am wondering what happens when you sync other programs/hardware to ardour? Are there any issues with Midi Clock? What happens when you get a signature change from one denominator to another in two programs - a sequencer with the 'other' convention and ardour? Maybe this isn't an issue anyway because sync is performed with absolute time?

drmoore
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further: just looking at midi clock information and would I be right in saying that they assume 24 MIDI Clocks in every quarter note?

seb: I am not talking about the metronome clicks here. I would expect the metronome to pulse in accordance with the current time signature.

paul
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ardour doesn't sync to MIDI clock. the sync options it has all involve non-musical time.

Pankot
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Yes, MIDI clock is fixed at 24 pulses per quarter note (crotchet)
http://www.borg.com/~jglatt/tech/midispec/clock.htm

tgoose is right that BPM is not really a formal concept. In those modern scores that give a numerical tempo indication, this is now done by something like "[crotchet] = 110" or "[quaver] = 90" where the bracketed entity is the actual symbol. In a compound time like 12/8 you would see the "beats per minute" referenced to a dotted quaver.

The widespread use of BPM came in with early drum machines and their use in disco and later dance music. For the first time it was meaningful to put a precise indicator on a label of the music's tempo - useful for DJ's trying to assemble a set list. Since 99.999999% of dance music is in 4/4, there was no need to reference the BPM figure to a note length - crotchet was implied.

Moreover, drum machines always referenced their "BPM" setting to a crotchet. Anyone used to programming a Roland would expect the transition from 4/4@120 to 4/8@120 to be a switch to double time feel, and probably describe it like that.

It probably comes down to the backround from which one arrives at a DAW. Ex-beatbox programmers (like me!) instinctively "see" a numerical tempo indication as defining the crotchet. You might say our brains work in MIDI Clock. :-)) Someone with a formal music background might well see it differently, more in line with the current Ardour implementation.

However, this could be resolved by just making the beat indication clearer. The issue, to me, is more one of workflow. If I want to insert a bar of 7/8 into a stream of 4/4, it is almost certainly because the effect I want is the "surprise" of a missed half-beat. I'm really inserting a bar of 3.5/4! At present, to get the correct effect, dmoore and I have to insert tempo changes either side - otherwise, the bar will sound to the listener as one of 7/4 with a half-time feel.

So, if it proves to be too difficult to offer two different modes of operation within Ardour as regards the meaning of "BPM", then another tack to take is to simplify the above task, by providing the means to automatically add the necessary tempo changes. All this needs is for the project to have an idea of "prevailing denominator" (= that at the start) and, upon inserting one more measures with a different denominator, to offer the option of a "fudge factor" associated with that measure that frobs the BPM so as to maintain a constant crotchet (MIDI clock) size.

drmoore
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Spent some time talking to 2 of my colleagues who are very experienced instrumental composers and they feel the same as I do. I got the impression that they would prefer to always see bpms marked with a denomination (like you might in a score). So at each tempo change you tell ardour what length a beat is.

I've done a simple patch for the backend, Tempo, Meter and TempoMap classes that makes ardour work the way I expect (currently defaulting tempo to quarter notes, but with a view to gui selection). Basically it adds a member var _note_type to the Tempo class and reworks the frames_per_bar and frames_per_beat functions to take a tempo (beat size) into account. I was going to look at adding a denominator dropdown to the tempo dialog so that you can specify what value the 'bpm' is based on. Is anyone interested in this? Patch is highly untested as yet but I would be very willing to put more time in if its likely to be a feature people want.

What's the normal procedure for patch submission or review?

drmoore
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Added the gui features to the tempo dialog and uploaded patch into mantis issue 0000940 hope this is ok.

Any feedback welcome.

paul
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an improved version of drmoore's patch is now in svn for branches/2.0-ongoing and will be in the next release.