First of all, there are two effects available in the Command Stations at all times, regardless of whether you're only playing a single Preset, or a Pattern with 16 Tracks playing at once. You can use the effects in two main ways, each selected from the Global menu. The first way is where the active Preset you're playing controls what the effects will be, and therefore all the effects settings are stored with that Preset. This way works best if you're only playing a single Preset at a time, from a master keyboard in a live situation, for instance.
The second way of using the effects is in Master Effects mode. In this case, all Presets share the same two effects, and the effects and all their settings are saved as part of each Pattern. However, being able to only turn the effects on or off for each part is not very flexible, so E-MU uses effect Sends to increase your options with only two effects. Just like there are only two effects for the entire Command Station, there are only four Sends for the entire unit as well. The send amounts for each effect are freely assignable in the Global menu. Here's an example of how they work: For instance, say your first effect is a reverb, and your second is a delay. You can specify how much reverb you want to be applied to Send 1, as well as how much Delay you want to be applied to Send 1. Say you set your reverb amount to 5% on Send 1, and your delay amount to 27% on Send 1. In this configuration, any Track you route to Send 1, will have about 5% reverb on it, and then it gets about 27% of the delay effect added to it. Simple, huh? If you only wanted reverb for instance, you would just set the delay amount for that Send to 0%, and now all Tracks routed to Send 1 will only have reverb applied. BTW, you can assign more than one Track to a Send, and you've got 4 Sends to use for your whole Pattern, giving you lots of ways to use only those two effects processors.