Much, much simpler method: Hold phone up to the source and play track while in “custom” and “record.” Some degradation of quality of course. Life full of trade offs.
The availability of APIs for speech-to-text functions, including Google AI, have allowed phone service providers to easily integrate voicemail transcription at a low cost and without much overhead. Transcriptions can be completed on the fly, so customers can expect access to their transcripts immediately following the receipt of an inbound call.

Here's the problem with recording elaborate joke messages on your answering machine: Your answering machine will become more popular than the person who owns it. Friends would tell total strangers to call my number and listen to the new goofy message. They would become disappointed if I actually answered the call first. I would have to hang up and let the machine pick up just for other people's entertainment. Dozens of people were finally calling my home phone, but few of them wanted to talk to me personally.
Professional voicemails are important, because they’re an extension of your personal brand, reflecting what level of professionalism you offer. Use these voicemail greetings for work or personal cell phone messages for your specific needs. You can choose a voice that will best suit your business and will deliver a warm and professional voice message. Your callers don’t want to hear a cold and indifferent machine voice. The information you want to put in your voicemail should be succinct enough for your callers to get every bit of information they need. Leave the relevant information in a clear and precise manner. Professional voicemail greetings for work should be informative. The first message the customer hears should have the company’s name so they can be sure they’ve reached the right number. Be courteous and informative. This could be their first point of contact, and you want it to be enjoyable. You may also like 30 Best Wishes and Congratulations for New Business Adventures If you’re going to make your voicemail message humorous in some way, it should be tasteful and aligned to your brand. It shouldn’t get in the way of giving customers enough information when they call. Your voicemail greetings for work should be welcoming and friendly but not too informal. Customers want to feel confident that they’ve contacted a professional, that the company values their call, and they have made the right choice. So be friendly but not too nonchalant. Your voicemail greeting should be clear, concise and to-the-point. You don’t have to put your clients through a sales pitch when they are trying to just get some information.