Hello jd. You don't need to find the centre of each note. Just one note will do - to help you discover what it is like to play in sympathy with the horn. I would suggest starting with second line G. You can find the sweet spot or slot with the main tuning slide in any position. In fact I encourage my students to do this. Start with the slide fully closed and dp the bending excersize to home in on the loudest pitch. Then to move the slide half an inch or more further out than normal and agaimn home in on the sweet spot. One of these notes will be very sharp, one will be very flat. Then you can take a tuner if you like and play the G bang in tune on the meter, with your slide pushed all the way in. To do this you will obviously have to bend the pitch doen below the sweet spot on the horn. The sound will be flabby, dull and lifeless. Then play in tune with the tuner with the slide in the extended position - by lipping the note up. The sound will be thin, strained nasal and lacking in vibrant over tones. Both these notes will require a lot of air to get a decent volume. By experimenting in this way and by gradually reducing the distance that you move the slide you can home in on the correct position where the sweetspot is in tune for the G. Now unless you have a perfect trumpet - which does not exist - some notes will be high and some low - so your tuning slide position is a compromise. However experimenting with the slot or seewt spot might lead you to some suprising discoveries, or inspire some fresh thinking about your playing, which is never a bad idea. I recently began to feel that when I make ajustments to my slide it is not because I am out of tune. There is really no need to ever be out of tune on a trumpet - we can bend the notes so easily. But I will make ajustments to the tuning slide if i feel that I am slightly off the sweet spot, that I am working too hard to be in tune or I am not really happy with the resonance of my sound. Have fun experimenting and let us know what you discover. All the best. Noel.