I can't see songs on my smartphone that are from the music library on my computer

Try the following:

• Verify that both the BlackBerry Desktop Software and your iTunes library or Windows Media Player library is open on your computer.
• Verify that the correct music library is selected in the BlackBerry Desktop Software. Click Device > Device options. On the Media tab, if the correct music library isn't selected, in the Music source drop-down list, click the music library that you want to use.