I had fun with the original eJay back in the 90's and bought this version in the sale. Firstly I'll assume you've already read the product description and mention a few other things you might want to know. eJay Dance 7 was originally released back in 2007 by the now defunct Empire Interactive. It only supports 2 video resolutions, 1024x768 and 1280x960, so you'll be getting black bars or borders if your system uses some other resolution. For me at least the program runs fine on 64bit Windows 7, there is a demo out there if you want to be sure it will run for you. eJay Dance 7 does not support MIDI input (or output). It also does not support VST or DirectX plugins, so you cannot use third party effects or instruments, nor can you use the supplied plugins with other software. I have to assume that when the description refers to "effects...with the ability to add more..." they are either referring to combining effects or to some eJay specific add-on that is currently unavailable.
So what you have here is a "walled garden", a stand alone piece of software dedicated to creating loop based dance music. If you wish, you can import sounds from CD, your PC's audio inputs, or as wave files, and you can export wave files of either loops or a whole track, but that is it, and importing your own samples as wave files could be easier, thankfully someone has posted a tutorial on You Tube. The advantage of this approach is that everything included just works, no faffing around with drivers and MIDI settings required.
Where eJay Dance 7 really shines is as a way of playing around with music. All the provided loops are in the key of C, and the supplied virtual instruments can be set to only play in this key too. This means you can just dive in, have fun, and stand a good chance of coming up with something that actually sounds like music. Although importing loops can be awkward, everything else about the user interface design seems good, it's attractive and I was able to find my way around most functions pretty quickly. The extensive tool tips really help here, and you can switch them off once you know what you are doing.
The program is also ideal for learning about music technology. You have all the basic effects units, a bassline synth, a polyphonic lead synth, a drum machine, and a loop sampler. It seems that every virtual knob and switch has a tool tip, and a more detailed explanation in the compiled HTML help file. In fact, when it comes to explaining what the effects and instruments do and how to operate them, this manual is one of the clearest I have ever read.
As a serious piece of music software eJay Dance 7 has some uses, but also limitations. You could certainly use it to create a soundtrack for a game or video, or to make a backing track for playing along to when practising an instrument. However the included loops are frankly a bit average, importing your own samples is possible, but not as simple as it could be. The quality of the effects and instruments is good, but not great. Overall I just wasn't quite convinced by the sound quality. Still you can't expect a £20, easy to use, dance music creator to compete with dedicated music production software.
I've given eJay Dance 7 four stars, it's well made, a great way of having fun with music, and of learning some of the basics of music production. Add a star if you can get it at a good discount.
