Mac (G4) Garage Band; singing

[Greegor]

I'm new here. Hi, y'all. I've just started in this home recording thing. I have a Tascam DP 01FX 8-track that I'm delighted with, and I'm doing drums on a Roland TD-6KV that I got from Saigon. Guitar is a Fender Telecaster, and the bass is a Paul Reed Smith OLP 5-string. Keys are a cheesy Chinese Medeli mc-80 with GREAT sounds on. I don't even know what the mics are - I got them in a package deal with the Tascam at Guitar Center - one mic for instrument mic'ing and one for vocals. Whatever. Everything is awesome.
Two problems, and any advice would be great. One, I have some stuff I can't play. Now, years ago I had a Yamaha CX-5M computer that had a great sequencing program that let me plug in the note values, voice (say, bass guitar), and tempo, key, notes, etc. and then I hit a button and the computer would play it. Far out, right?
Well, is that sort of thing possible with the Garage Band program on my laptop (iMac G4)?

Also - I always thought I had a decent enough voice - I've sung back-up and occasional lead in live situations, while playing drums. So why do my vocals suck so bad on my own recordings at home? I can't seem to hold the right note. It sounds good while I sing, and on the headphones, but on playback, I hit sour note all OVER the place. What's up with that? Do I actually suck, or am I doing something wrong?
Thanks in advance for anything any of you may have to say.
Greegor

 

[jimmy2sticks]

Garageband: Not featured enough to do what you describe here. You can plug in a MIDI controller and play with the patches, but is as far as it goes.

Singing: It seems perhaps you can't hear yourself well enough while singing. Either that or your breath support is lacking. Are you holding back in your studio?

Also, have you ever heard a recording of your live vocals? I have worked with singers before that tell me the same thing, but when I see them live there are still far from in tune.