Depends on your workout and preferred music choices. I love a bit of rock, punk and metal, plus I'm on a rowing team, so I've tailored mine pretty specifically.
Need to get pumped? Anything by
Sabaton ( try
Masters Of The World) or
Hatebreed (
I Will Be Heard and
In Ashes They Shall Reap are particular favourites) will do just that.
Slayer are also pretty damn good for lifting. I also use a combination of them for my 2k test on the erg (rowing machine), a fast enough drumbeat to smash it to and angry lyrics to help you push.
For cardio, I'm only really used to cycling, which I do outside and have no music for safety on the roads, or the erg again, where I've found
Ramones can help keep you between rate 18 and 24 for long sessions to build stamina. Naturally, out on the river I wouldn't risk my iPod to the weather and water, plus I need to hear what the coach is yelling at me.
As for your weight loss goals, I don't know what you've got in mind, but once you've got the technique down, most Concept rowing machines have a setting for 500m sprints with a 60 second rest, try not to drink or stop in the rest; just slow right down to recover,without feeling the pain of stopping completely. Do that frequently, around 2pm if you can for maximum effect (apparently), and you'll be well on your way, it's what I did and do, and while there hasn't been much weight loss, the muscle:fat ratio has definitely changed. Plus you get ridiculous legs. Everyone loves good legs.
Edited with song names and fabulous photo.