Practicing tuning with a pitch drone is one of the best ways to improve your intonation. Using a tuner is also important when practicing, however a tuner provides visual cues to indicate if you are sharp or flat. In rehearsal and performance the tuner won’t be helpful and the ear will be the only guide. A drone provides an audible pitch reference which trains the ear. The best tool that I have found to use for a pitch drone is the Tonal Energy app. Tonal Energy not only includes a pitch drone function, but also a metronome, tuner, and the ability to record and analyze pitch tendencies.
The sound setting allows you to choose sounds on a wheel, guitar, or piano. I find it easiest to use the piano setting and to change the transposition to accommodate the clarinet I’m playing. Tonal Energy also allows you to select a drone sound. I prefer a sound that is rich in overtones, this helps to hear the pitch before you play it on your instrument. The saw wave and organ sound settings provide the most harmonically rich tones. Next you will need to select the temperament. I typically use just intonation rather than equal temperament. In equal temperament, not all intervals are truly in tune. For example, if you play a third in equal temperament you will hear beats. In just intonation all the intervals will be in tune. I use the equal temperament if I will be performing with piano because the piano uses this intonation. Lastly for set up, I amplify the pitch drone using an external speaker. I find the speakers in my iPhone and iPad too quiet to play with.
The best exercise for practicing intonation with a pitch drone is slow long tone octaves. I set Tonal Energy to sustain octaves on the pitches I will play. Then I will start low, move up an octave, then return to the lower octave. Before moving to the upper octave I ensure that I’m hearing in my mind the upper pitch. If there are any inconsistencies in pitch I will repeat this exercise until the pitch is accurate. If I’m having trouble hearing the pitch I’m moving to, I isolate that pitch on tonal energy and match it on my clarinet, then set octaves in the app and return to the original exercise. I play octaves chromatically ascending the full range of the clarinet ensuring each interval is in tune. This exercise can also be repeated with other intervals. The best progression is to start with perfect intervals (8ve, 5th, 4th). Once you move to non-perfect intervals you need to make adjustments for accurate intonation (i.e. major 3rd will be flat and minor 3rd will be sharp in just intonation).
There are other pitch drones that can be used, but I have found Tonal Energy to be the most useful. A free pitch drone can also be streamed on YouTube.