What type of activities or thoughts other than the actual recitation of shema, tefillah, etc. are not consisted a pause? For example, it seems that kohanim chanting during birkas cohanim would mitigate there being time that elapses without them actually uttering the Bracha (ע’ מ”ב ס’סה ס”ק ד)
Anything which is for the purpose of increasing concentration, or inspiration in Tefilla would be permitted. This would include tunes commonly sung, pausing for contemplation, or even to clear one’s mind.
See Igros Moshe O:C 3:8, Aruch Hashulchan 128:35, SHevet Halevi 5:15.