The advent of technology has drastically transformed the landscape of music education, particularly in regards to piano instruction. The shift from traditional face-to-face tutoring to online piano teaching has engendered both opportunities and challenges for both instructors and students alike. In retrospect, there are several aspects about online piano teachers I wish I'd comprehended fully prior to engaging their services; insights that would have informed my decisions and optimized the learning experience.

Firstly, the pedigree of the online piano teacher is paramount. This goes beyond their academic qualifications or prowess as a pianist. Look for instructors with a proven track record of successful online teaching, as pedagogical strategies for online instruction significantly differ from those of conventional, in-person teaching. The efficacy of the Zone of Proximal Development, a prominent educational theory proposed by psychologist Lev Vygotsky, is contingent on the teacher’s ability to scaffold instruction to bridge the gap between a student's actual development level and their potential development level. This strategy might be compromised in an online setting if the teacher lacks the necessary skills and experience.

Secondly, an understanding of the technology platforms used by online piano teachers is essential. Various platforms such as Skype, Zoom, or specialized music teaching software have their respective strengths and drawbacks. For instance, assessing sound quality, a critical aspect in music instruction, might be compromised on certain platforms due to compression algorithms. Therefore, it is important to have a basic understanding of these platforms to ensure the technology facilitates rather than impedes the learning process.

Thirdly, the concept of asynchronous learning is central to online piano instruction. This refers to the ability of the student to access learning materials and exercises at their own pace, a key advantage of online learning. However, its effectiveness is heavily reliant on the teacher's ability to provide comprehensive learning materials and clear instructions, thus underscoring the importance of the teacher’s online teaching skills once again.

Fourthly, the possibility of lagging motivation and engagement is a potential downside in online piano teaching that needs to be mitigated. Social Interactionist Theory, another core concept in psychology, highlights the importance of social interactions in learning, which can be diminished in online learning. Therefore, an online piano teacher needs to employ innovative strategies to foster engagement, such as interactive games or collaborative assignments with other online learners.

Furthermore, flexibility, one of the leading selling points of online piano lessons, can also present a drawback. The lack of a fixed schedule can lead to procrastination. A savvy online piano instructor should demonstrate astute time management strategies that ensure consistent progress.

The sixth point revolves around the financial implications of hiring an online piano teacher. While online lessons are generally more affordable, there are hidden costs such as the investment in a good quality piano, internet connectivity, and the necessary software. Conducting a cost-benefit analysis prior to commitment is advised.

Seventhly, the lack of immediate physical correction in technique is another limitation in online instruction. Teachers must therefore employ descriptive language, demonstrations, and possibly video analysis tools to ensure correct technique.

The eighth point is the need for students to be more autonomous and proactive in their learning. Self-Determination Theory, a model of motivation, suggests that autonomy can enhance intrinsic motivation, which is beneficial for learning. However, this also means that the student must take on a greater responsibility for their own learning.

Ninthly, the access to a global network of teachers can be a boon. However, considerations such as time zone differences and language barriers must be taken into account when choosing the right instructor.

Finally, it is crucial to remember that online piano lessons may not work for everybody. Students with learning challenges might struggle with the format. Therefore, it's essential to assess whether online piano lessons are the right fit based on individual learning styles and needs.

In conclusion, hiring an online piano teacher can be a gratifying undertaking if navigated with an understanding of the inherent strengths and challenges. With the right match and the appropriate expectations, the world of music can be unlocked from the comfort of your home.