The journal will be a place to keep all of your IB day-to-day, logs of work in progress, coursework, ongoing recordings and more.
Which format would best suit your learning style?
Electronic journals - i.e OneNote
Blog/vlog
Website
Paper journal
Another form
You should journal after every exercise/rehearsal/performance done in class or at home
Keep the sections clear - perhaps one for each component (Exploring, Experimenting, Presenting and Contemporary Music Maker (HL only)) or one for each role (Researcher, Creator, Presenter) - take care to ensure each piece within each role is clearly linked to the components
Make sure you know which Area of Inquiry is linked to each journal entry
Use different forms for recording notes - docs/video/audio
Tag or link each entry to help pull together your final submissions
Cite every link clearly at the time of finding - this will make your bibliographies easy to write.