The number is
Each line of the poem
corresponds to an odd member of the harmonic series. The first couple letters of the line represent the solfege of that pitch. Some of the harmonics are kind of weird or "alien".
Do whatever you want to play
The first harmonic is the fundamental represented by Do.
Solution is one step away
The third harmonic is the fifth scale degree or Sol.
Mine for alien harmony
The fifth harmonic is the third scale degree or Mi.
Take some notes you want to declare
The seventh harmonic is a weird flat seventh scale degree. A major seventh would be ti, a flat seventh can be represented by te or Ta.
Regions you were so unaware
The ninth harmonic is the second scale degree or Re.
Fundamental is always there
The eleventh harmonic is a weird sharp fourth scale degree. A perfect fourth would be fa so a messed up one could be Fu.
Lurking frequencies over it
The thirteenth harmonic is another weird one. It's close to a flat sixth scale degree. A regular sixth is la so a weird one could be Lu.
Tiny steps between for the fit
The fifteenth harmonic is a relatively accurate leading tone or Ti.
Radiating sounds are so lit
The seventeenth harmonic is a flat second scale degree or Ra.
So what next?
The solution is one step away. Mine for alien harmony.
The next odd harmonic is the nineteenth harmonic which is a sharp second or flat third scale degree.