I suppose he means a masalla in general. Garam is a mixture of spice mixes and can be a sauce or just mixed powdered spices. In my store cupboard I have fish massala.
Allspice,cinnamon,nutmeg are used extensively in Carribean cooking.
Jeera, Cardamon,chilli,Tumeric, and many more are seasoning spices in Indian food.
Ras el Hamout is a North African spice mixture used in Morroco.Basically it's a pot pourri if various blends.
I don't believe there are definitive seasoning spices. Lets not forget that Indian cooking is very much regional as to the ingredients and spices used. It's a question of take your pick mate depending where you are and what you are cooking. I reckon your Indian chef was talking spices in general.
I agree that almost without exception a blend of aromatic spices sprinkled on at the end is the best for seasoning , garam masala is my ideal and I haven't tried many variations.
I simply think that it's because a single spice alone can be harsh.
I use garam masala as a spice to sprinkle on food at the end of cooking, I also sprinkle freshly chopped coriander and or spring onions at the end too. Garam masala is a mixture of 'warm spices' (pepper, dry coriander, jeera seeds, cinnamon, nutmeg etc) rather then hot spices (chilli)In my opinion Garam masala, if used too generously, it can spoil the flavour of a curry. The mixture can vary but above are the basic ones included. Jackie hth