I picked up the GB-10 last week. I got confused between the models and thought that this had the bass removal feature but it doesn't. Feel kind of foolish, but that's not going to influence the review I got it the GB-10 to slow down songs so that I could practice. For that, it's pretty good. You can alter the speed of songs by +/- 50%. It does that without altering the pitch. It does this by grabbing a slice and repeating it. You can hear that pretty easily in the song - it comes across as a wavering effect. On some songs (eg, Tom Sawyer), it makes the drums sound terrible. Other songs (eg, Drives Me Crazy) come out okay. I think that it's related to how much reverb there is in the mix. You can also change the pitch. You can shift it up or down almost an entire octave, going up and down a key at a time. Pretty much everything I played with it sounded like blue cheese (you know, just a bit funky) but the pitch was on. The GB-10 comes with a standard jack, so I plugged in the bass and started playing. I noticed right off the bat that I could not actually hear the bass until I set the input level to 9 or 10 to hear my bass. It's passive and I had the bridge set to 80% and the neck to 30%. There is an input meter on the display, so I could see that I was getting signal. I just couldn't hear anything. First thing I checked was my headphones. I piped the output through the stereo and confirmed that it's putting out sound on the low end, so I know that my headphones were part of the problem. That didn't surprise me - cheap headphones don't carry a lot of bass. Then I remembered that I had set the output to minimum because when it plays an MP3, it is extremely loud. Sure enough, turning up the output level gave me sound. And it sounded pretty good, too. Naturally, the next thing that I tried was playing along with a song. That was one big ouch. Turning up the volume increased the level of the bass but it also increased the volume of the song. That was painfully loud. After going back to the owner's manual (there's a quick start in it but you'll have to go through a lot of the sections carefully to figure out what some of the buttons do), I discovered that the balance is what you have adjust. I thought that it was "left to right," just like on the stereo. Nope. It is the mix of input to song. The default is set to the maximum, which is about 95% song. I think that I've mentioned that is pretty loud. I suggest turning it down to about 50%. For reasons that are probably clear to the engineers at Tascam, the range is from 1 to 20. Set to 10 when you first start using it and work it from there. I turned the balance down to 8, which is about 60% input, 40% song. That seemed about right. It also functions as a recorder. You can record solo or overdub. I thought that the reproduction in solo was pretty true. I like the tone coming out of my Jazz and this created a very faithful WAV file. When I listened to a recording, I found out that the balance of 8 was actually too much bass. I get the feeling that I will be forever tweaking the balance. That, in my opinion, is the biggest flaw with this unit. I don't like playing with the balance on every single song. Maybe I wouldn't have to do this if I let iTunes set everything to the same level. I'm not cool with that for general listening but it may be something that I do just to get along with the GB-10. Anyway, I played a song at 50% speed and recorded it. You can record as a solo or as an overdub. I was wondering what it would sound like when played back since it was at 50%. When I played back at 100%, I noticed that the GB-10 did a good job of recording and converting my line to the right speed. I haven't tried recording at 150% speed, though. The unit has some built in effects. You can change the amp and cab settings, adjust the "tone" and add reverb or some effects like wah, chorus and tremolo. There is also a built in compressor. You can change the amount of compression, the attack and volume. None of these were very impressive. They're not meant to replace the real deal, but, if you're on a bus and bored, they're fun to play around with. You can save your settings to the memory card for later recall. One more thing - I did verify that you can use this with classical music, too. Now I can actually play along with the Suzuki recordings for violin. The unexpected thing is that the speed change "tremolo" effect sounds pretty good on these recordings. Edit - I didn't mention it but you can use the amp settings to bring out the bass. I was able to get acceptable sound out of the buds that way. Still no substitute for good headphones.