StaffPad uses its own, unique handwriting recognition engine. Once you become familiar with the recognition system, writing music with StaffPad becomes fast and fluid - but, depending on your writing style, you may find you need a bit of patience at first as you get used to the system.
If you're finding the app isn't recognising your handwriting, there are a few common and easy things you can try which may improve your results.
As with any recognition based system, a certain degree of accuracy and penmanship is required to get the best results. The system is built to be quite tolerant - but there are definitely some ways to adjust your own writing style slightly to work best.
First, make sure you've looked at the examples in this article about writing notes and rests
It's also worth watching the video tutorials found in the "Discover" section of the app, especially on writing music.
Here's some general tips to help improve recognition:
1) Use a simple diagonal line for a note-head, rather than the coloured in "blob" style. Make sure the note-head only covers one line or space.
2) Make sure your lines are straight for stems and beams. Wavy lines may get misinterpreted as slurs or other elements. It can help to use one ink stroke per element (i.e one stroke for the note-head, one for the stem, one for a beam etc)
3) Use multiple passes. When you first start with StaffPad, it can be really helpful to use multiple passes at a bar to get all the elements together. Start with just a few notes and rests, then tap out side the bar to recognise it. After it's recognised, go back and add more notes, articulations and dynamics and so on. By breaking down the bar into a few elements, you'll quickly gain better accuracy - partly because the rendered notation exists to help align elements and place things correctly within the bar, but also because it reduces the possibility of errors in each pass.
4) Zoom out and write quicker: this may sound counter-intuitive, but the app was actually designed to be used at relatively small staff sizes for fluidity and speed. If you're writing zoomed in, however, do remember to make your notation larger to match the scale. StaffPad is relatively tolerant to size - but it works best if you write notation at the scale it'll be when it's rendered.
5) Don't bunch up notation in the bar. You can simply drag the bar-line out to the right if you need to make more room to work. StaffPad will have trouble with recognition if your music is bunched up within the bar.
6) Erase and clean up any mistakes within the bar. StaffPad actively looks at every ink marking in the active bar. If you have any other markings that were unintentional - for example, if you've crossed something out, or traced over something twice, or have some unnecessary ink strokes in the bar - then StaffPad will leave the bar pending rather than try and delete those strokes for you. It's always best to clear up the bar and erase unwanted or unneeded strokes before you tap out side the bar to recognise.
If the bar turns orange once you tap outside the bar area, this means it's "pending" - which means that the app is simply asking for clarification. You can try deleting a few ink strokes that look a bit "off" and redrawing them - there's no need to redraw the entire bar.