Hello,
I have a question thats become a growing curiosity for me.
What dictates what speed vs. tempo you will use. From my knowledge I guess you could attain similar BPM’s with a high tempo, and lower speed setting or vice a versa. Is it the actual loops or samples that you employ that dictate the decision for you, or a stylistic thing, dictated by the “resolution” you want in a song, like using the 9xx will sound much different in certain instances with high speed vs. low.
Thanks a lot.
Generally, BPM is used as your intended tempo while Speed dictates resolution. There are really no set rules however, so try different things. Some people swear by fast (numerically low) Speeds while others (or at least IT-Alien 
) likes to drag it down as much as possible.
Personally I like a faster scrolling pattern for more agressive or lively music and a speed at around 6 or 8 for more ambient and downtempo tracks.
Speed alters tick based effects…
For instance, retrigger. With a speed of 6 you have 6 triggers, with a speed of 3 you have 3. With a speed of 1 you have 1 value.
With delays (i.e. 0Dxy) it will work only if xy is less than the speed. If your have a speed of 6, telling Renoise to delay a note 8 ticks is meaningless and won’t work.
Thanks a lot guys, that cleared things up for me.