Hi ! I appreciate you have written your requirement very nicely. Its really hard to find detailed requirement on freelancer now days anyways :) I have gone through your requirement. Let me tell you what I understood .
Features needed
-One Person at a time sings over a beat, then the others get turns- 1 min each -ok
-import sound file for beats/music - ok
-choose premade beat - ok
-admin panel backend-ok
-each battle or rap session can be saved to phone or pc - file downloadable - ok
-social share or basic social integration (not a focus) - ok
your idea is for a rap freestyle app and website where people come to ---live -in -real time--- rap with each other, one person holds the mic or gets to go at once while others listen (chypher) or rap battle
things "MAYBE" needed:
✔ Video/audio streaming, codec: Wowza, Red5, , MPEG-4 - ok
✔ VOIP, Cloud Communication: Twillio, Heroku, Tokbox -ok
✔ Online Payment Gateway: PayPal, , Stripe, Venmo, Braintree, Payleap -ok
✔ Facebook, Twitter, Linkedin, Instagram, Youtube, Pinterest, Vimeo - ok
✔ Cloud backend: , Parse SDK, Parse REST, Parse Cloud Code, Amazon S3 EC2 AWS, Firebase - ok Foodie, remoteStorage, Twillio, Plivio - ok
✔ Chat & Messaging Engine: XMPP, Jabber, OpenFire, OpenTok WebRTC, Ejabberd, Erlang -ok
Lets discuss more over Chat box,
Waiting for your precious response!!
*Placed bid is not the final one, It can be revised after final discussion.
Regards,
Abhi.