Symphony is described as 'Chat, SMS, and share all of your files all in one place. Perzo is the secure and more productive solution to your communication needs' and is an website in the Social & Communications category. There are more than 10 alternatives to Symphony, not only websites but also apps for a variety of platforms, including Windows, Android, iPhone, Linux and iPad. The best alternative is Element. It's not free, so if you're looking for a free alternative, you could try Tox or Jami. Other great sites and apps similar to Symphony are Threema (Paid, Open Source), ChatSecure (Free, Open Source), Wickr (Freemium) and Bit Chat (Free, Open Source).
Element is a secure collaboration and messaging app based on the Matrix protocol. It’s decentralised to deliver digital sovereignty, and based on an open standard for easy connections and interoperability. It is end-to-end encrypted by default.
Jami (formerly GNU Ring, SFLphone) positions itself as a potential free Skype replacement Open Source and cross-platform. Jami gives you a full control over your communications and an unmatched level of privacy.
ChatSecure is a free and open source messaging app that features OTR encryption over XMPP. You can connect to your existing accounts on Facebook or Google, create new accounts on public XMPP servers(including via Tor), or even connect to your own server for extra security.
Technitium Bit Chat is a secure, peer-to-peer (p2p), open source instant messenger designed to provide end-to-end encryption. It can be used over Internet and private LAN networks for instant messaging and file transfer.
Off-the-Record (OTR) Messaging allows you to have private conversations over any instant messaging (MSN,Gtalk, Facebook and so on) by providing encryption, authentication, deniability, perfect forward secrecy
Librem Chat – end-to-end encrypted chat, VOIP, and video calling used by millions of people * Chat rooms * Share images, videos, and files * Make voice and video calls * Keep your conversations secret with end-to-end encryption * Free and open-source software