Usually when someone says doubling ' ruined their embouchure ' what actually happened is they didn ' t practice properly as a doubler . Firstly , when you add a new instrument you need to treat it ' s practice as a separate thing from your existing one . So if you practice 30 minutes a day on trombone right now , you can ' t go 15 trombone and 15 trumpet and expect to stay as good on trombone , you need to go 30 trombone and whatever you decide to do on trumpet . Also you should practice the swap . That ' s what makes you an effective doubler , is being able to swap quickly between two instruments but many people don ' t practice it . Play an exercise on trombone , then on trumpet , then another one on trombone , then another on trumpet , etc .