If your DX7 is not responding to parameter changes, make sure that memory protect is turned off. From the manual:
- Press the 'Memory Protect' [INTERNAL] button. The display will read 'MEMORY PROTECT INTERNAL ON'.
- Press the [-1/NO/OFF] button. The display will read 'MEMORY PROTECT INTERNAL OFF'.
- To exit from the Memory Protect mode, press the Memory Select [INTERNAL] button.
NOTE: The Memory Protect setting will automatically reset to 'ON' every time the keyboard power is turned off and on again.
For more resources related to this synth, read our Yamaha DX7 Resources page.