Logic Pro 9 MIDI not sounding

Pam S

New Member
Just starting to work with Logic 9 (v. 9.1.3) after a long break; using iMac w/OSX 10.6.6, Firebox, & Glyph 500 GB HD (not even close to full). I used Sonar for years, took a break and am now trying to learn the idiosyncracies of Logic because I much prefer using a Mac! A painful experience!
I've been working thru tutorials in the Apple Pro Training Series for Logic Pro 9 and when I added added MIDI voicings, they worked ok...at first. However, when I add certain instruments I hear them when I record, but they don't sound on play back. One was a bass line, which wouldn't play back til I raised it an octave - not good if I want the lower pitches. The other was a bell sound that won't play back regardless of the octave. These are the stock sounds that came with Logic, haven't loaded (or tried to load) any new sounds...yet.
Any suggestions? Please...