Question about looping software

[Sean Onion <sean@zwieble.com>]

Newbie here... short question is this: I'd like advice about Apple based 
s/w that can do live looping.

About a month ago I walked into Guitar Center and walked out with an 
RC-50.  I brought it home, played around, researched on the net, found 
loopers-delight and read all the archived comments, then played some 
more.  Resolved all the issues to my own satisfaction (hiccup, feedback, 
modes, they're mostly solved by system level settings) and had a blast 
playing around and being creative.  Only thing I didn't solve for is the 
one thing that RC-50 simply can't do: loops under 1.5 seconds.  So I 
took it back and traded for a Vox ToneLab SE modeller.  12AX7/ECC83 dual 
triode, and up to 4 seconds looping; more along what I was looking for 
when I walked into GC. 

At any rate, the RC-50 turned me onto something I never thought I'd 
enjoy so much... looping phrases (as in long patterns, entire sections 
of a song, etc.)  I've played around with Garage Band and BIAB, so I'm 
familiar with using drag/drop loops to build a song.  But being able to 
do it live, on the spot... it's addictive!  I'm exctatic with my new 
modeller, but I want to also start playing around with this. 

So this is what I'm thinking.  I've got an older i-Mac with OSX 10.2.8, 
1Gb ram, 130Gb disk and an Oxygen-8 USB midi keyboard.  I looked at 
Ableton Live but the current version is as much as the RC-50 so I don't 
think I can afford that route in the short term.  Plus, in my experience 
there are sometimes open-source s/w that are as good as or better than 
commercial software. 

As to hardware, I supposed I could use Intel based stuff but I love the 
Apple so much.  Frankly, it's quieter, both electronically and audibly.  
I've also got a Mac Mini, but isn't that more geared as an office 
workstation?  Beyond that, I'm clearly over my head and out of my league.

I'd like to hear from you as to what I should do.

Sean