I’m sure I’m missing something completely obvious or have gone about this totally the wrong way! 
But I’m just messing around with some basic riffs to practice being creative and decided to tab them out in Guitar Pro however one of them works out to be (in 4/4 timing) 3 bars of eight 8th notes and one bar of five 8th notes so 2.5 beats.
Is this wrong? Can I do that? (Guitar Pro doesn’t like it! 
) Or is my time signature / division of beats wrong? Or should I change the riff to fit? 
Actually, I have done the last, sort of at least, I changed it so that it’s 3 beats, so 3 bars of 4/4 timing and one bar of 3/4 timing. But I think I preferred it when it was 2.5 beats? 
I’m sure I’m being a complete noob here! 
Any guidance greatly appreciated! 
Mmmm. Bit hard to comment without seeing the score. Any rests or 8th note triplets in there you may have missed.
Just throwin ideas around.
Cheers, Shane
I was worried someone might say that It’s very simple stuff so was hoping to avoid sharing but I could understand it’d be tricky without seeing/hearing it. So this is what I was messing around with… Just the beginnings of an idea and I’m sure ripping off a hundred songs! 
This is 29 beats across 4 bars. 29 is a prime number so cannot be divided by anything to get a whole number of notes. You cannot represent this in 4/4. You will need to have at multiple time signatures with at least one odd-time bar. Like this, for instance:
This works and is entirely valid in GuitarPro, but also is musically valid. It is, however, highly unusual and, I would suggest, indicates a mistake somewhere.
Note that it’s not uncommon to have a single bar of a different key signature between song sections, such as a bar of 2/4, but it’s not usually a repeated part of a verse or chorus. For example, this song (in 4/4) switches to 2/4 for a bar between sections:
Odd time or unusual patterns of time signatures can be made to work, but it’s usually a lot more difficult than standard 3/4, 4/4, or 6/8 as it’s not something people are used to hearing.
Cheers,
Keith
That makes a lot of sense, Keith, thank you! So I’m thinking I could play it on a guitar but a drummer would hate me, right?!
The other thing you can do, if this is a repeated riff and you like the slightly disjointed rhythm, is to keep the bar length at 4/4 and to repeat the sequence offset from the start of the bar, like this (i’ve used different frets to indicate where the pattern repeats):
In this case, I put a half note at the end to complete the bar.
Cheers,
Keith
Ah!! So if I did the whole pattern repeated 4 times, that would be 29*4 = 116 (8th notes) then that would equal 14 bars at 4/4 and 1 bar at 2/4? Which would work! Maths!! 
That depends on the drummer. Some would take it as a challenge.
Odd time signatures are more common in some styles of music, especially Progressive Rock and Metal. Bands like King Crimson, Rush, and Genesis have quite a few in their catalogue. Notable ones include:
Rush - Freewill (13/4)
King Crimson - Discipline (17/16 hands over a 4/4 bass drum)
Dave Brubeck - Take 5 (5/4)
Allman Brothers - Whipping Post (11/8)
Some of these can be jarring, and deliberately so. Others can be surprisingly musical.
Genesis were,in my opinion, masters of making odd and varying time signatures sound musical and non-obvious, until you try to count them out. Some great examples here include:
Dance on a Volcano
Firth of Fifth
Apocalypse in 9/8
The last of these is, fairly obviously, in 9/8. The first two vary the time signatures quite a lot. (Firth of Fifth, by the way, has probably my favourite guitar solo of all time).
Also, Turn it On Again, which was a top-10 pop chart hit in the 1980s, has a time signature of 13/4.
But another notable song you might want to consider is:
Metallica - Master of Puppets (3 bars of 4/4 and one of 5/8)
Cheers,
Keith
True! Either that or they’d throw a drum stick at me!
Some great tracks you’ve listed there, some I know and others I need to check out, especially this one below!
I tabbed it out over 15 bars, with the last being 2/4 and that actually works how I had it in my head, so… that’s awesome! Thanks again!! 
Although will probably mix up the power chords at the end of each rotation to make it a bit more interesting… just small steps for now though… 
Best listened to with headphones, by the way. Also, this may interest you if you like the song:
Cheers,
Keith
Absolutely , yes, there’s even a song on the App that has a short measure mid song. 
Dont ask which one as I dont recall the name at the moment ok.
Yeah, that was brilliant! And that solo was immense, those builds and prolonged notes, just great, I can see why it’s a fav 
Loved her analysis, the idea of the song’s elements painting a landscape, really works. And her insights on the tonal variations of the solo are gold (the guitar being a saxophone, clarinet, bagpipes, etc! ), hadn’t heard it that way but she’s right Thanks for sharing, Keith!
Jeffs riff has a major MoP vibe so sounds that the 3 bars of 4/4 and one of 5/8 is probably the right time signature?
Hmmm good point JK I’ve chucked some drums over it in that configuration to see how it worked. Apologies, I have no idea what I’m doing with drums though 
Sounds good Jeff! A fill in the odd bar is the way to go 
I’ve been reading along (beyond me to comment), Jeff, and have to say with a little work on the guitar tone (I assume this is GP not you playing) and I would be quite convinced it was a Metallica song (I only know a few songs from the Black album).
I heard a bit of Vicarious by Tool in it. Sounds cool!
Thanks David, I’ve no doubt ripped it off someone subconsciously and I have listened to a ridiculous amount of Metallica in my life, so I’d not be surprised if their DNA showed up all over riffs that spill out of my head 
But the fact that you’ve actually thought there might be some similarities is huge to me actually, very happy about that! Thank you!
This is all still in it’s infancy though, although maybe I can take it somewhere…
Edit: forgot to say, yes it’s GP doing guitar on the YT recording above
Ah! That’s interesting, Jeff! Tool actually sprung to mind to me as well when I was messing around with it, funny! I’m not sure I have a deep enough well of emotions or dark visions to do anything that comes close to Tool , but I have spent a significant amount of time digesting their back catalog too over the years, perhaps some that might filter through?
Hey, the pots in your witch’s kitchen are bubbling as I can see…
I recently had a related question as your initial one, good to see, that I’m not the only one…
Btw, sounds really good, even to my non metal ears, like the added drums… 