Phrase block loop

another missing thing in phrases other than Phrase sustain is the ability to define a block loop, how it is possible in standard patterns.

the problem here is that you don’t always want a phrase to restart from the beginning once it has reached the end; a typical scenario is when you have created a phrase which is actually a sound design rather than a real phrase: in such cases, you most likely would want the phrase to continue indefinitely rather than retrig its notes from the beginning.

consider the following scenario, where a C-5 with oscillating volume is added to the standard C-4 note:

## note vol note vol   
00 C-4 -- C-5 00  
01 --- -- --- I2  
02 --- -- --- I2  
03 --- -- --- O2  
04 --- -- --- O2  

you would like the phrase to loop indefinitely from 01 to 04 rather than restarting from 00 once 04 has finished playing.

another more flexible solution could be adding ZBxx ZE00 commands, where xx is the number of repetitions (00 = infinite), similarly to how it was in Fast Tracker II

## note vol note vol comm  
00 C-4 -- C-5 00 ----  
01 --- -- --- I2 ZB00 <= loop start (00 = infinite loop)  
02 --- -- --- I2 ----  
03 --- -- --- O2 ----  
04 --- -- --- O2 ZE00 <= loop end  

of course you could work around this problem using the tedious and limiting approach of using extremely long repeating pattern in the phrase, but you easily understand that this is not the best way of doing it…