in this series of videos I'll be explaining what time signatures are and how they work in this video part four I'll be explaining the following irregular time signatures and I'll be demonstrating how to calculate missing time signatures from a passage of Music in part two I discussed how to calculate whether a time signature was simple or compound and whether it was duple triple or quadruple it it's not quite that straightforward with irregular time signatures let's have a look at 58 to start with as you're watching this video which is part four of the series of videos you should now be able to look at this time signature and immediately be able to identify that it means five qu for beats per bar however how many pulses are there in each bar well there's actually two but they are not the same in length a bar in 58 can either be a crotchet pulse followed by a crotchet or the other way around whichever way around they are placed the bar will still equal five Quavers but because the crotchet can be split into two equal parts which would indicate simple time and the dotted crotchet into three equal parts normally compound time it's absolutely impossible to State whether the time signature is compound or simple it's for this reason that this type of time signature is called irregular or sometimes it's called uneven or asymmetrical each bar contains both simple and compound divisions of the pulse staying with 58 for the moment it's important to note that the pulse is either crotchet then dotted crotchet or the other way around it can never be Quaver crotchet crotch it or any other combination of these notes even though each of these examples equals five Quavers per bar even in irregular time signatures there will always be a pulse and each pulse must split into a combination of twos and and threes the lone Quaver is not allowed as a result even though 58 is an irregular time signature and therefore not simple or compound is it duple triple or quadruple well it's actually none of them now you might ask why is it not dupal as there are two pulses in 58 well it's because each pulse is not equal calling 58 dup would suggest two equal beats it is therefore a quintuple time signature Quint Tuple meaning five I'll add this name to the time signatures at the top of the screen let's look at another quintuple time signature 54 which has five crotchet beats per bar I've always found 54 a strangely satisfying time signature and two famous pieces of music that spring to mind which use 54 very effectively are Mars from the planets by Holst and the theme tune to the original series of mission impossible not the film version with Tom Cruz as that moves into 44 after about a minute now I can't show or play the music here for copyright reasons but do look them up on YouTube and listen and feel the unusual beat of five crotchets per bar like 58 there are two pulses in 54 either a minim and a dotted minim per bar or vice versa as the pulse does not split neatly into equal groups of two or three it cannot be simple or compound thus making it an irregular time signature as I said earlier the five beats also means that it is a quintuple time signature the other type of irregular time signature you're likely to come across are septuple time signatures an irregular time signature with seven beats the most common are 78 and 74 seven Quaver beats and seven crotchet beats in each bar respectively there can be three pulses in 7 eight and they are a combination of two groups of two Quavers and one group of three the groups can appear in any order such as these and can even change between bars if the two groups of Quavers appear next to each other they can even be Bean together like the first four or the last four Quavers in a bar of 4 four this does change the pulse to just two per bar very occasionally you might see this instead of 78 it actually means the same as 78 as 2+ 2 + 3 equal 7 but it is clearly telling the musician that each bar has three pul is divided into two Quavers two Quavers and then three Quavers you won't be asked about this if you're sitting an Associated board music theory exam but it's worth knowing as this type of time signature does pop up every now and again finally 74 has the pulse divided up into minim minim dotted minim or like 78 any order of these pulses before we finish let's have a quick look at a typical question you might come across in a music theory exam your job is to select the correct time signature the first thing to notice is that bar one starts with a group of three Quavers bar two ends with two groups of two Quavers as there is a mix of groupings of twos and threes we're clearly dealing with an irregular time signature if we can just Inc crotch it so assuming that the time signature has a four at the bottom bar one has a value of three and a half therefore we're clear clearly not supposed to be dealing and counting in crotchets because remember the top number has to be a whole number let's try Quavers so an eight at the bottom of our time signature there are three Quavers at the very start of the bar the next two crotchets both contain two Quavers each therefore there are seven Quavers in the bar we've already deduced that the answer to this question would be an irregular time signature therefore we pop the seven at the top of our time signature our answer is 78 I do hope that this video and the entire series of videos on time signatures has been useful to you I'll be uploading some new videos very soon so please do keep watching