Try to use char pointer notation (char *) instead of array notation (char[]) in structure declaration:

struct commands
{
    int   cmd;
    char*  descr;
};

• OR -

use struct declaration as-is, but change the array initialization like below:

commands cmds[] =
{
    {16, {"Hammond Organ"}},
    {17, {"Percussive Organ"}},
    {18, {"Rock Organ"}},
    { 0, {""}}                   // end of list marker 
};

Additionally, it seems that it always should be written as:

struct commands cmds[] = 
{
    // here your code
};

If you have disabled warnings in your compiler, enable them again - and try to write program the way that you will newer receive warnings.

Try to use char pointer notation (char *) instead of array notation (char[]) in structure declaration:

struct commands
{
    int   cmd;
    char*  descr;
};

• OR -

use struct declaration as-is, but change the array initialization like below:

commands cmds[] =
{
    {16, {"Hammond Organ"}},
    {17, {"Percussive Organ"}},
    {18, {"Rock Organ"}},
    { 0, {""}}                   // end of list marker 
};

Additionally, it seems that it always should be written as:

struct commands cmds[] = 
{
    // here your code
};

If you have disabled warnings in your compiler, enable them again - and try to write program the way that you will newer receive warnings.

Thanks for your answer. It helped me a lot.

There must be something wrong with the simulator (Simulator for Arduino - version 1.11E Designed by Virtronics). In the meantime I received the Mega 2560 board and both char pointer notation (char ) and array notation (char[]) work well with the board. The compiler (Arduino IDE v. 1.8.10) really produces warnings: ISO C++ forbids converting a string constant to 'char' [-Wwrite-strings]. Perhaps the simulator is more meticulous than the compiler and therefore refuses to work with a code thar generates warnings.