In my career as a professional musician, I've rarely performed with an accompaniment CD or tape. There were a few exceptions, like the time I played Diane Thome's "Like a Seated Swan" with a recording of computer-generated sounds, but for the most part, accompaniment meant a live pianist. So when I started teaching, that's how I taught my students. I'd play with them on a duet part, or we'd have a piano accompanist. However, I quickly realized that both of these methods have limitations.
When I accompany my students on duet parts, I have to look at my own part. That divides my attention, so it can be hard to focus on my student or help them get back on track without stopping our performance. As for piano accompanists, they're often only available for one rehearsal before a student performs. That means that the student doesn't have much of a chance to practice with the accompaniment before a performance, and they don't have the benefits of regular accompaniment in their lessons. To address some of these problems I decided to try having my students play along with a recording.
While I've often used recordings as a reference in my lessons, and I've always encouraged students to listen to excellent music, I'd previously been reluctant to have them actually play with an accompaniment CD. Until recently, I found there were many drawbacks to recorded accompaniments. The CD or tape only played at one tempo, which was often far too fast for a beginning student. However, there are several music apps available now that will slow down or speed up a recording without distorting its pitch. I used one of these to set appropriate tempos for my students, and gave the recordings a try. I've been very happy with the results. Since recordings are less "sympathetic" than a teacher or a pianist, they often help a student stay in tempo or play rhythms accurately. It's like a metronome with chords!
Furthermore, hearing the chords and accompaniment improves students' intonation as well. They can match pitch to their part if it's included in the recording, or they can hear how their notes fit into a chord. The accompaniment can help students listen closely, and it gives them something to compare themselves too.
Of course, many of the recorded accompaniment parts are also fun to play along with. They may have parts that sound like a full orchestra or a band instead of just a piano. One student I had loved playing the “Star Wars” theme to an accompaniment that sounded like it came right out of the movie.
Although I was initially skeptical of recorded accompaniments, I'm glad I gave them a try. I still think it's important for students to play with live pianists, and I still play duets with them, but I've discovered that recorded accompaniments are useful tool for teachers—one that's available for every lesson.