How to Play Complex Polyrhythms and Odd Time Signatures on Guitar
An odd time signature like 7/8 or 5/4 isn't mechanically exotic - it's simply an uneven grouping of beats inside a bar instead of the familiar 4/4 or 3/4. A polyrhythm is a different thing: two different pulses sounding at the same time (three even beats over two, for example). Both show up in real music, but they're practiced differently.
An odd meter is a grouping, not a mystery
7/8 is almost always counted not as seven identical beats in a row, but as groups within the bar - 3+2+2 or 2+2+3, for instance: 'one-two-three, one-two, one-two.' Counting in groups instead of individual beats is the only practical difference from the familiar 4/4.
Set the metronome to the actual bar length
In the app, open the metronome (the Metronome tab, see the article on time signatures), set 'Time signature' to 7, the beat subdivision to eighth notes, and turn on the accent on the first beat. The accent confirms where each bar starts, but the metronome doesn't lay out the 3+2+2 grouping inside the bar itself - you count and emphasize that yourself.
3-over-2 polyrhythm: count against the faster pulse
To feel 'three against two,' set the metronome to click on the faster, three-part pulse, and count or tap your foot on the slower two-part pulse yourself - the app's metronome only gives you one shared click; you hold the second, overlapping grid on your own. Start by just clapping the slower pulse over the metronome's clicks before bringing the guitar in.
Drill: a familiar phrase in 7/8 instead of 4/4
Take an already-familiar pentatonic phrase (see the article on getting started improvising) and play it as exactly seven eighth notes instead of the usual eight - without changing the notes themselves, just cut the bar one eighth note short and restart the repeat from there. It is the fastest way to physically feel what makes 7/8 different from 4/4 without learning new material from scratch.
Essayez-le en pratique
Open the metronome