I have an ESQ-1, and I’m wondering if I can replace the battery without losing all the internal programs.
If you have any custom programs, you will definitely want to save them first. Replacing the battery will cause the ESQ either to revert to the factory programs, or it will show BRASS1 in all 40 program locations, depending on which OS version you are using.
If you have an OS version earlier than 2.30, then you will get BRASS1 everywhere. If you have 2.30 or later, you will get the factory default programs - and if that is all you are using, you may not need to save your data first.
Note also that you will lose any sequencer data when the battery is replaced, so you’ll want to save anything important there also.