Taken from K2600 Musician's Guide, page 6-9:

While you are scrolling through different programs on various MIDI channels, you may occasionally encounter a program that doesn't make any sound, and whose name is in parentheses. The parentheses tell you that you have seleted a KB3 program without being on the KB3 channel. KB3 programs use a different program architecture, and require many more voices to operate. Consequently, they need a special channel with enough throughput to handle those voice requirements. If you select a KB3 program without being on a KB3 channel, the K2600 cannot play the program.

The Program-mode page illustrates this in two ways: the program names are in parentheses, and the box at the left of the page includes the message "KB3 Chan is Ch 1". To fix this, you could either change the K2600
s MIDI channel (with the Chan/Bank buttons), or make Channel 2 the KB3 channel (using the KB3Chan parameter in Master mode).