To just keep your strings in time with all the other instruments, you may have to pull their start time a little bit back from the beat you want them to play on.In the first picture the notes are all aligned right with the beat. One of the hard things with strings and quantization is that the samples don’t always start playing right at the beginning of your MIDI note. You don’t want to quantize your notes so that they begin right on the beat – about 80-95% is a good place to stay. The key to improving the realism of your MIDI string sounds is to humanize them – so you change the velocity, and you change the quantization. (In Garageband I think the preset is 98.) Varying your velocities within about plus/minus 15 steps is a safe place to keep it so that you get variation, but it still maintains a similar intensity.
Just like with MIDI drums, to make your MIDI strings sound most realistic, you shouldn’t just keep all your notes’ velocities at the same level. It’s not sold anymore, but you can pick up copies online of the Symphony Orchestra ‘Jam. Garageband already has, whilst it’s a small limited amount, a nice selection of quite authentic instruments, like strings, pianos and other world-instruments. Orchestra Strings Spiccato & Legato 1 - 4.
Create movie sound tracks that’ll send a shiver down your spine with these creepy orchestral horror music loops for Garageband.
That being said, there are ways to help make your MIDI strings sound a little bit less pathetic and a little more realistic in your mix.