A lot of folks use their computer
as their MIDI sequencer
. This saves them a lot of money
versus a stand-alone sequencer, and it allows them to upgrade as newer technology
Many keyboards have built-in sequencers, albeit limited versions. Sequencers based on software and a sound card or dedicated MIDI card are low-cost, high-quality solutions to assembling an inexpensive music studio.
When buying sequencers, look for the following items:
Try to get sequencers that work well with other systems and software. Sequencers that let you assign patches using names rather than MIDI channels and program IDs can help reduce errors and confusion. I personally use Cakewalk, but there are a large assortment available. Read before buying: Thomas Dolby, for example, once said, "You can tell an amateur by looking at their hard drive and finding Cubase."
If it's not upgradeable, you're stuck with it. You will end up tossing it in a closet when you need something that is more up-to-date. Save your money, get something that can be made useful over and over again.
Being able to view notation, or even better being able to print a copy, lets you view and archive lead sheets.
You will find it is faster to hit alt-S than it is to use your mouse. When working with a tune, don't get distracted trying to surf your mouse pointer to a particular spot... just use a keyboard shortcut. Learn them, for they are your friends.
Save some cash, buy a used version if you can. This will allow you to get better hardware with the savings. Look at places like eBay or other auction sources.