If you just want instructions on how to jam successfully and in sync, then please read this post first. If you want to really understand jammr and how the Beats Per Interval (BPI) value affects synchronization, then keep reading this post.
How does jammr work?
A short introduction for all new jammr users.
jammr is a program with which you can jam together with other musicians. It's all live, but not in real time. We play interval-based and this means that everyone will only hear the other users' intervals when it is “done” (if you watch the metronome, you can see when a new interval starts, namely when the first one starts blue block lights up).
For this reason it is not - or only very difficult - possible to play longer chord sequences or entire songs.
It makes sense to set an interval to the length (BPI = beats per interval) that is needed to play a part, a chord progression, a loop, … 16 BPI corresponds to 4 bars in 4/4.
There is a nice explanation: https://forum.jammr.net/topic/1115/
If you have problems with the settings: https://forum.jammr.net/topic/4/
Good examples of playable songs are e.g. Zombie by Cranberries, Wicked Games - Chris Isaak, 9 Crimes - Damien Rice … (3 - 4 chords the whole song) for 16 BPI.
For 32 BPI more songs are possible: e.g. Knocking on heavens door, Nobody knows you - E Clapton,
A blues standard usually has 12 bars → 48 BPI. Here it is important to find the “first blow” and stick to the sequence. If something changes during the interval, it no longer fits the others and sounds terrible. It is very helpful if someone - preferably the drummer - has an overview and the beat begins on the metronome for the first beat of the interval. Using the metronome, everyone can see when “it starts all over again”.
Of course, simple jamming in one key is also possible, and changing the chord progression is possible if all participants are attentive and withdraw so far that everyone gets their space. A BPI of 16 is advisable.
Otherwise you will find many questions in the forum and often good answers, mostly from very nice people.
Before you log in, please check that your microphone is muted or that you only have headphones as the playback source. Then it does not happen that you ruin the ears of other musicians (who mostly use headphones …) ;-)
I hope this little introduction is helpful and understandable for you!