Greetings:

I present two code fragments:

 

(setf val 256)
(setf mat1 (sieve-tree 8 2 5 :rnd-order NIL))
(setf stream (make-omn
:length mat1
:pitch '(c4)))
(setf out (omn-to-measure stream '(4/4)))

 

This evaluates to:

(q c4 mf c4 3h 3q_3q 3h q_3q 3h 3h 3q_7q 7h. 7h. q_3q 3h_3h 3q_3q 3h 7h. 7h. 7q_3q e 3e_5q 5w_7q 7h 7h 7h q_3q 3h_3h 3q_7w 7h._7h. 7w_3q 3h 3h 3q_7q 7h. 7h. 7h. 7h. 7q_e. s. s s s._7w 7h._7h. 7h. 7q_7h 7h 7h 7q_5q 5h. 5q 3e 3e 3q 3q)

 

Here is the OMN stream (stream):


When written to the variable "out" using omn-to-measure the result is the following:

 

 

Here is another code fragment:

(setf mat2 (flatten (gen-loop 8 (gen-tuplet 1 3 'd 'n 'q '(5 3 4) :times 2 :omn t :seed val))))
(setf stream2 (make-omn
:length mat2
:pitch '(c4)))
(setf out2 (omn-to-measure stream2 '(3/4)))

This produces the OMN stream (stream2):

Which outputs to "out2" as follows:

 

 

I am  hoping someone can enlighten me as to my mistakes with the first code fragment.

With thanks!

Use alway quantize function with complex lengths:
 

(setf val 256)
(setf mat1 (sieve-tree 8 2 5 :rnd-order nil))
(setf stream (make-omn :length mat1 :pitch '(c4)))
(setf out (quantize (omn-to-measure stream '(4/4)) '(1 2 3 4 5 7 8)))

 

So helpful!  Thank you!

 

The third line of code creates a notation with 4/4 measures throughout.

 

The final line of code produces a 31/32 measure at the end.  Probably due to the fact that the mat1 call does not create an "even" number of events.