There are different Arthanusandhaana Vidhis in Brahmi:
3. Uddeshaartha / Apekshartha
4. Aagneyaartha / Krutyartha
A single mantra of Veda is a combined form of these 6 Arthas. It will be integrated with special Chando Rahasya also. Rigveda has 8 inclusions for each mantra:
A Rigvedic Mantra is not effective without explicitly pronouncing the triplet of Rushi, Devata, Chandas. Other 5 will be included in Mantra itself. Jagadguru Shankaracharya who realized the Prakruti told that "Aadau Pranavamuccharya". Veda itself has the Prakruti. So Omkaara has to be prefixed to Mantra.
Saama Veda has Swara-Saptaka, means 7 divisions. Basically Saama Swaraas are of two types: Madhyama, Mandrastaaraka. 7 x 2 = 14 + Anunaasika at Starting & Ending = 16 Swaras are decided by Saama.
Shukla Yajurveda also says about 7 Swaras. Shukla Yajurveda is made of 2 divisions in which the (Proved) Shruta Bhaaga are 6. Seventh one has not been revealed. Taittariya Krishana Yajurveda gives 4, as moola yajurveda text is not available.
These are some of the keys to understand the meaning of Veda Mantras.