The most common codecs are G729 (compressed) and G711 (non-compressed). They are designed to compress human speech, and often cause a loss of audio fidelity — which is worse in some languages than others. On hold music that has been specifically designed for that purpose, to be used with VoIP systems and codecs, can sound great. But it is not easy to come by.
source: I have a android with version 2.3.6 is it possible or is there a app to play music to the calling person when you place a call on hold? francos Level 1 (Contributor) lissa.meeker Level 1 (Contributor) "But you can not just play music if your on the phone...."

Though it can be convenient and cost-effective, don’t let Bob from the copy room record your telephone voice messages. Phone communications represent a crucial component of a successful business. Whoever you pick will become the voice of your brand and business. When choosing a voice for your on-hold recordings, your target audience should be the most important factor. Who would one of your prospective clients take advice from? Who would they find the most captivating and trustworthy? Whether they’d prefer a conversation with a friend, command from an authority figure or advice from their mom, keep your audience’s needs at the forefront when listening to voice samples. Concept & Copywriting Directing & Producing Latest Audio Formats I'm a small business. Do I need professional recorded messages? Yes, you do! The size of your business has no bearing on its quality and professionalism. Whether you have a team of 200 employees or you're the one and only, having a professionally recorded message puts your business in a different category. This level of quality and attention to detail is a testament to your professionalism and dedication. On-hold programs vary from industry to industry. A doctor may tell you what insurance coverage they accept, while an auto body shop may want to share directions for after-hours drop-off information. Regardless of your industry, there are a few things all businesses should consider including in their on-hold program: Of course! In most case, we do recommend the use of music. Music is essential to most productions. At Migrate Sound, we spend countless hours looking for the right piece of music. When the music is right, your audience will go from being interested to being attentive and absorbed into your story or message. This is a subjective matter and can only be answered comparatively with other businesses providing the same services. We are probably more expensive than those online services. Some of these guys will sell you a fully produced message for $25. That said, we are definitely less expensive than those large Hollywood studios who charge a whopping $350 an hour. We are a small business in Santa Clarita, California. We care about the quality of our product, and more importantly our clients. We're happy when you're happy and we will do whatever it takes to get you there. Audio is our business and we've been doing it for many years.
We offer affordable rates. That way, you can take care of your clients and get set up with a custom phone message that doesn’t break the bank! Our goal is to ensure that your clients’ time on hold is being used to your advantage. That’s why we make sure that creating a custom hold message is affordable and fits your budget. Simply get in touch with us and we’ll help you find the best on hold message or music that still works for your company’s monetary needs.