I use Amazing Slow Downer and think it is great. I just tonight played from Marc Savoy's CD "Ameded Two Step" which is in the key of B-flat. By moving the ptich on ASD up 2.0 units it changes into the key of C, the same as my accordion. So you can not only slow it down but also change the pitch of a tune.
You can try out ASD form the above web site to see if you like it before buying it. Roni does give good support to his products.
I also use Audacity to record as I practice. It is free! form the above web site!!! and well worth looking at. You can make mp3 files and if you play the guitar make a track for the accordion and one for the guitar plus several other instruments. It's unbelievable and free.
I just downloaded the Audacity, I had n-tracks before which costs around $60. It works ok but the Audacity seems to be more user-friendly. I'll let you know once I try it.
I so agree with Ed here. There is no learning curve. Change the speed ,change the key. Pick out 3 bars over and over , 10 seconds in between. Slow it down 10% Take out the bass side get the words that you can't understand. Good support, they have improved it. Works on Mac. Just what us music junkies always wanted. Jerry
I have used a tascam (about $159)to slow down, change keys, and maybe best of all, loop segments to play a bazillion times over.
You just pop in a cd and go. It takes a bit of fussing with it to figure it out, but not bad.
I haven't used mine in quite a long time, but I used to.
You could check on ebay. Zzounds.com is a good co. to check out for this type of stuff, and I have found that they have good reviews on lots of gear.
I usually use Sound Studio. Pitch and speed are tied together, which isn't what you always want. There is a 'fader' you can slide to zone in on the pitch; Getting that Bb flat tune to match you C accordion. If you change pitch by 100%, you'll get half the speed and one octave lower, cool for trying to figure out all those tough little licks.
Steve